The custom Windows argument-comment-lint job was temporarily moved to
`windows-2022` in #28940 after hermetic LLVM source extraction failed on
the newer runner. This takes the upstream extraction fix so the job can
return to the intended custom runner.
This upgrades `llvm` to `0.7.9` and `rules_cc` to `0.2.18`, refreshes
the module lock, rebases the remaining Windows and custom libc++
patches, drops the obsolete symlink-extraction workaround, and restores
the `windows-x64` runner configuration.
Validation:
- Verified all LLVM patches apply cleanly against the `0.7.9` source.
- Built `@llvm-project//compiler-rt:clang_rt.builtins.static`.
## Why
Windows ARM64 uses 64-bit `long double`, but the LLVM MinGW Bazel
configuration omits the upstream `powl` compatibility source and does
not link the `mingwex` archive that owns it. Cross-linking the release
binary therefore fails with an unresolved `powl` symbol.
## What changed
Patch the LLVM module to compile `math/arm-common/powl.c` into the ARM64
MinGW extension sources and add `-lmingwex` to the Windows toolchain
defaults.
## Validation
- `just bazel-lock-check`
Stack: 3 of 6. Depends on #27322.
