LLVM prebuilts 22.1.7

[codex] Support distributed ThinLTO on macOS (#617)

This adds distributed ThinLTO for macOS targets after #615. The existing
`windows-thin-lto.patch` remains unchanged, and the macOS rules_cc
changes are isolated in `macos-thin-lto.patch`, which is applied after
`windows-thin-lto.patch`. The macOS patch corresponds to
bazelbuild/rules_cc#748 and only adds Mach-O LLD's direct distributed
ThinLTO arguments.

The LLVM source patch adds the exact-file `--lto-obj-path` contract
proposed upstream in llvm/llvm-project#203365. The exact-file contract
lets the indexing action produce rules_cc's declared
`thinlto_merged_object_file` without reproducing Mach-O LLD's
`0.<arch>.lto.o` directory naming.

`is_windows_capable_of_thinlto_feature` and
`is_macos_capable_of_thinlto_feature` default to false and independently
control whether the toolchain exposes the rules_cc `thin_lto` feature on
Windows and macOS. `windows_capable_of_thinlto_feature` and
`macos_capable_of_thinlto_feature` combine the corresponding build
setting with the target OS constraint. `--config=prebuilt` enables both
build settings. `is_windows_capable_of_thinlto_feature` can be removed
after a rules_cc release contains Windows distributed ThinLTO support.
`is_macos_capable_of_thinlto_feature` can be removed after rules_cc and
LLVM releases contain macOS distributed ThinLTO support. The previous
macOS `-flto=thin` fallback is removed because rules_cc now creates
separate indexing and backend actions.

Validation:

- Applied `windows-thin-lto.patch` followed by `macos-thin-lto.patch` to
a clean rules_cc checkout and compared the resulting ThinLTO feature
with the rules_cc source.
- `bazel test
//tests/rule_based_toolchain/legacy_features_as_args:thin_lto_macos_test
--test_output=errors` in rules_cc.
- `bazel build --config=prebuilt --config=remote --config=bootstrap
//prebuilt/llvm:for_windows_amd64 //prebuilt/llvm:for_windows_arm64
//prebuilt/llvm:for_macos_amd64 //prebuilt/llvm:for_macos_arm64`.
- BuildBuddy invocation:
https://app.buildbuddy.io/invocation/ff484673-abb8-41c9-ba4c-a19410241625