[CI] Add build configuration with clang to post-commit CI (#3040)

Author: Alexander Batashev

.github/workflows/linux_post_commit.yml

@@ -26,7 +26,13 @@ jobs:
                  export ARGS=""
                  ;;
              SharedLibs)
+                 wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
+                 sudo add-apt-repository "deb http://apt.llvm.org/bionic/   llvm-toolchain-bionic main"
+                 sudo apt-get update
+                 sudo apt-get install -y clang-12
                  export ARGS="--shared-libs"
+                 export CC="clang-12"
+                 export CXX="clang++-12"
                  ;;
              NoAssertions)
                  export ARGS="--no-assertions"

sycl/cmake/modules/AddSYCLUnitTest.cmake

@@ -36,6 +36,13 @@ macro(add_sycl_unittest test_dirname link_variant)
       ${SYCL_SOURCE_DIR}/source/
       ${SYCL_SOURCE_DIR}/unittests/
     )
+  if (UNIX)
+    # These warnings are coming from Google Test code.
+    target_compile_options(${test_dirname} PRIVATE
+      -Wno-unused-parameter
+      -Wno-inconsistent-missing-override
+    )
+  endif()
   # LLVM gtest uses LLVM utilities that require C++-14
   # CXX_STANDARD_REQUIRED makes CXX_STANDARD a hard requirement.
   set_target_properties(${test_dirname}