[libcxx] [ci] Run the libcxxabi and libunwind tests in mingw configurations

[mstorsjo]

Summary

The check-runtimes function runs check-cxx, check-cxxabi and check-unwind.

This still depends on D147638, D147640 and D147860. (check-unwind
should already be passing, while the three remaining patches makes
check-cxxabi pass too.)

[ldionne]

That's nice!

[mstorsjo]

Rebased on latest git main; all dependencies should have been merged now, so I'll merge this if CI still is passing.

libcxx/utils/ci/run-buildbot

mingw-dll)
     # environment has got two installations of Clang; the default one
     # defaults to MSVC mode, while there's an installation of llvm-mingw
     # further back in PATH. By calling the compiler with an explicit
     # triple prefix, we use the one that is bundled with a mingw sysroot.
     generate-cmake \
           -DCMAKE_C_COMPILER=x86_64-w64-mingw32-clang \
           -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-clang++ \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake"
-    echo "+++ Running the libc++ tests"
-    ${NINJA} -vC "${BUILD_DIR}" check-cxx
+    check-runtimes
 ;;
 mingw-static)
     clean
     generate-cmake \
           -DCMAKE_C_COMPILER=x86_64-w64-mingw32-clang \
           -DCMAKE_CXX_COMPILER=x86_64-w64-mingw32-clang++ \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake" \
           -DLIBCXX_ENABLE_SHARED=OFF \
           -DLIBUNWIND_ENABLE_SHARED=OFF
-    echo "+++ Running the libc++ tests"
-    ${NINJA} -vC "${BUILD_DIR}" check-cxx
+    check-runtimes
 ;;
 mingw-dll-i686)
     clean
     generate-cmake \
           -DCMAKE_C_COMPILER=i686-w64-mingw32-clang \
           -DCMAKE_CXX_COMPILER=i686-w64-mingw32-clang++ \
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake"
-    echo "+++ Running the libc++ tests"
-    ${NINJA} -vC "${BUILD_DIR}" check-cxx
+    check-runtimes
 ;;
 aix)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AIX.cmake" \
                    -DLIBCXX_TEST_CONFIG="ibm-libc++-shared.cfg.in" \
                    -DLIBCXXABI_TEST_CONFIG="ibm-libc++abi-shared.cfg.in" \
                    -DLIBUNWIND_TEST_CONFIG="ibm-libunwind-shared.cfg.in"
     check-abi-list