As the preinstalled CMake on the windows-11-arm runners currently
is an x86_64 build, we need to explicitly specify
CMAKE_SYSTEM_PROCESSOR, and CMAKE_SYSTEM_NAME to make CMake
consider it a cross compilation (otherwise CMAKE_SYSTEM_PROCESSOR
gets overridden by CMAKE_HOST_SYSTEM_PROCESSOR, which gets influenced
by the x86_64 as CMake is running emulated).
We also need to set LLVM_HOST_TRIPLE, as the autodetection of
it relies on CMAKE_HOST_SYSTEM_PROCESSOR. The host triple needs
to be in normalized form with "-windows-gnu", otherwise a couple
dozens of tests fail.
We also include the AArch64 target, to make sure the built compiler
can generate code for the host.
Since 07bc54bf4554398b199f4dc849e5193b98422f23 in llvm-project
(May 5th), these tests should pass on aarch64 too.
This avoids relying on finding these dependencies in $PATH while
running the tests. Some tests may set PATH="" while executing them,
which previously caused those tests to fail in this build setup.
The same is not an issue with MSVC builds with
-DCMAKE_MSVC_RUNTIME_LIBRARY=MultiThreadedDLL, because those
DLLs are also available in global system directories (including
DLLs such as msvcp140.dll and vcruntime140.dll).
Ninja isn't documented as one of the tools provided by the CI runner
images, but it used to be available implicitly installed before
in the windows-2022 images. Since the 20230918.1.0 image update,
it no longer is available out of the box; see
https://github.com/actions/runner-images/issues/8343.
Martin Storsjö