Run PAL tests in CI

[am11]

We used to run PAL tests on every PR, somehow this got broken in the past and it is not clean to me when.

Originally posted by @janvorli in #34710

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Other notes:

• PAL tests build is currently failing on macOS. fixed by Fix PAL test build on non-Linux Unix platforms #35218.
• Given PAL tests are useful for new platforms bring up, where msbuild/dotnet(1) is not available; we should consider:
  • adding an option in src/coreclr/build-runtime.sh to build PAL tests OR
  • move PAL tests under src/coreclr/tests and add option in src/coreclr/build-tests.sh to skip everything that depends on msbuild/dotnet(1), and build only PAL tests.

[guesshe]

When I notice this issue, I set CLR_CMAKE_BUILD_TESTS in my CMake toolchain file. For each sub-project, I am currently maintain a toolchain file. I found it is flexible for me to do something in the toolchain file instead of modifying CMakeList.txt file that belongs to the folder.

[am11]

You can simply run:

./src/coreclr/build-runtime.sh -skipgenerateversion -nopgooptimize \
    -cmakeargs -DCLR_CMAKE_BUILD_TESTS=1

without modifying any file. But adding formal option in the script for PAL tests would be good (internally which can transform to the above).

[danmoseley]

Cc @janvorli fyi