Fix EHa flag compiler filtering

The previous attempt to enable Structured Exception Handling in
(only) MSVC using the /EHa compiler flag caused trouble with flags
defined with Cmake Generator Expressions. These expressions are
not fully resolved, and they fail validation checks in
check_cxx_compiler_flag(). The previous attempt at applying
/EHa to only MVSC involved refactoring a direct call to
target_compile_options() with a call to the Slang helper function
add_supported_cxx_flags() where an additional MSVC filter was
introduced, but the helper also calls check_cxx_compiler_flag() to
see if flags are supported. It was okay for /EHa, but not some
other flags that ended up getting newly validated.

The above issue is fixed by re-implementing the change that added
/EHa to only MSVC. This change goes back to adding compiler flags
without the helper function with its extra validation, instead using
an additional cmake generator expression to apply /EHa only to MSVC.

cmake/CompilerFlags.cmake

@@ -16,10 +16,6 @@ function(add_supported_cxx_flags target)
     endif()
 
     foreach(flag ${flags})
-        # /EHa enables SEH on Windows, it is not available in Linux.
-        if(NOT CMAKE_CXX_COMPILER_ID MATCHES "MSVC")
-            string(REGEX REPLACE "/EHa" "" flag "${flag}")
-        endif()
         # remove the `no-` prefix from warnings because gcc doesn't treat it as an
         # error on its own
         string(REGEX REPLACE "\\-Wno\\-(.+)" "-W\\1" flag_to_test "${flag}")

cmake/SlangTarget.cmake

@@ -337,10 +337,9 @@ function(slang_add_target dir type)
         )
     endif()
     if(ARG_EXTRA_COMPILE_OPTIONS_PRIVATE)
-        add_supported_cxx_flags(
+        target_compile_options(
             ${target}
-            PRIVATE
-            ${ARG_EXTRA_COMPILE_OPTIONS_PRIVATE}
+            PRIVATE ${ARG_EXTRA_COMPILE_OPTIONS_PRIVATE}
         )
     endif()
 

tools/CMakeLists.txt

@@ -276,7 +276,7 @@ if(SLANG_ENABLE_TESTS)
                 EXTRA_COMPILE_DEFINITIONS_PRIVATE
                     $<$<BOOL:${SLANG_ENABLE_CUDA}>:RENDER_TEST_CUDA>
                     $<$<BOOL:${SLANG_ENABLE_OPTIX}>:RENDER_TEST_OPTIX>
-                EXTRA_COMPILE_OPTIONS_PRIVATE /EHa
+                EXTRA_COMPILE_OPTIONS_PRIVATE $<$<CXX_COMPILER_ID:MSVC>:/EHa>
                 OUTPUT_NAME render-test-tool
                 REQUIRED_BY slang-test
                 FOLDER test/tools