[qt/clang/llvm]: Summary of bulk changes made

Git repository change summary for qt/clang/llvm
Pushed by mirror-service into branch 'upstream/users/arsenm/triple-cmake-system-name'.
Changed from 5c078516cefa0742e7c881de33f65086e105fafc to 59544e8e3e6fa313087decf9d6179aaa901e9117
Acknowledgement was received that this change introduces only existing code that has been pushed to another public open source repository.

This change contains the following new commits:

Git commit 59544e8e3e6fa313087decf9d6179aaa901e9117 by Matt Arsenault on 21/07/2026 at 22:05..
cmake: Derive CMake system name from a triple via new mechanism

This is a reimplementation of the cmake functionality first implemented in
6e4e181c83, which has now been reverted twice. Implement the raw cmake functionality
without introducing the uses yet.

The runtimes build needs to translate the build target (configured with a target
triple) to cmake's naming scheme, to use for CMAKE_SYSTEM_NAME. Use the OS/environment
list from TargetParser as the source of truth; add an additional entry for the
cmake name to ensure the build system and compiler always recognize the same set
of names.

Upgrade the previous cmake regexes to a new python script which parses the
authoritative def file. The new script logic should match Triple::normalize's
permissiveness for various legacy and malformed triple shapes. This should be
more maintainable than the previous cmake regexes, since there's now a unit test
mirroring the triple unit test.

Co-Authored-By: Claude (Opus 4.8) <[email protected]>
https://invent.kde.org/qt/clang/llvm/-/commit/59544e8e3e6fa313087decf9d6179aaa901e9117