add miri test docs - #86

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

generated from commit 65992ee

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims



We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35 
try-job: test-x86_64-gnu-aux

…r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux

Rollup merge of #165117 - RalfJung:skip_missing_miri_shims, r=maxdexh

std: use skip_unsupported_miri_tests to control when tests should be skipped in Miri due to missing shims

We currently run some subset of std tests in Miri, skipping some because Miri doesn't support the operations they need. That is based on filters in the makefile. People don't know what is actually being tested and add random `cfg(miri)` in places to disable tests that were never run. This makes it quite hard to track which tests are being skipped and which operations we should add in Miri to get 100% std coverage. So let's replace that string-based filter with a cfg flag, `skip_unsupported_miri_tests`, that can be annotated at the tests.

Unfortunately I can't figure out how to disable all doctests in a module based on a cfg flag, so this entirely disables std doctests being run in Miri in our CI. (We still run them in https://github.com/rust-lang/miri-test-libstd.)

See prior discussion [on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/219381-t-libs/topic/Miri.20vs.20tests.20in.20std/with/635913743).
Docs PR: rust-lang/std-dev-guide#86

r? @tgross35
try-job: test-x86_64-gnu-aux