Expand core::hint::unreachable_unchecked() docs
Rework the docs for `unreachable_unchecked`, encouraging deliberate use, and providing a better example for action at a distance.
Fixes#95865
Fix e_flags for 32-bit MIPS targets in generated object file
In #95604 the compiler started generating a temporary symbols.o which is added to the linker invocation. This object file has an `e_flags` which is invalid for 32-bit MIPS targets. Even though symbols.o doesn't contain code, linking these targets with [lld fails](https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/MipsArchTree.cpp#L76-L79) with
```
rust-lld: error: foo-cgu.0.rcgu.o: ABI 'o32' is incompatible with target ABI 'n64'
```
because it omits the ABI bits (`EF_MIPS_ABI_O32`) so lld assumes it's using the N64 ABI. This breaks linking on nightly for the out-of-tree [mipsel-sony-psx target](https://github.com/ayrtonm/psx-sdk-rs/issues/9), the builtin mipsel-sony-psp target (cc `@overdrivenpotato)` and probably any other 32-bit MIPS target using lld.
This PR sets the ABI in `e_flags` to O32 since that's the only ABI for 32-bit MIPS that LLVM supports. It also sets other `e_flags` bits based on the target to avoid similar issues with the object file arch and PIC. I had to bump the object crate version since some of these constants were [added recently](https://github.com/gimli-rs/object/pull/433). I'm not sure if this PR needs a test, but I can confirm that it fixes the linking issue on both targets I mentioned.
Gracefully handle normalization failures in the prospective inliner cycle detector
Preliminary work for adding the regression test in #96950 to our test suite (it was flaky on glacier).
If this PR solves the flakiness on glacier, we can then merge #96950
Add test of matches macro for trailing commas
Almost all macros are tested for trailing commas.
The macro matches! was however not tested.
This PR adds that test case.
Related to #46238
Clarify what values `BorrowedHandle`, `OwnedHandle` etc. can hold.
Reword the documentation to clarify that when `BorrowedHandle`, `OwnedHandle`, or `HandleOrNull` hold the value `-1`, it always means the current process handle, and not `INVALID_HANDLE_VALUE`.
`-1` should only mean `INVALID_HANDLE_VALUE` after a call to a function documented to return that to report errors, which should lead I/O functions to produce errors rather than succeeding and producing `OwnedHandle` or `BorrowedHandle` values. So if a consumer of an `OwnedHandle` or `BorrowedHandle` ever sees them holding a `-1`, it should always mean the current process handle.
Add compiletest and bootstrap "--skip" option forwarded to libtest
With this PR, "x.py test --skip SKIP ..." will run the specified test suite, but forward "--skip SKIP" to the test tool. libtest already supports this option. The PR also adds it to compiletest which itself just forwards it to libtest.
Adds the functionality requested in https://github.com/rust-lang/rust/issues/96342. This is useful to work around tests broken upstream.
https://github.com/rust-lang/rust/issues/96362#issuecomment-1108609893 is the specific test issue my project is trying to work around.
