[libspirv] Don't force fp16/fp64 OpenCL extensions (#18961)

Enabling these (or any extensions, really) by default is incorrect and
prevents the r600 OpenCL builtins from being built. Each clang target
reports which OpenCL extensions it does or doesn't support.

This commit also moves the flag enabling SPIR-V builtin declarations to
the SPIR-V options. They are not needed for the compilation of CLC or
OpenCL builtins.

There is no change to any builtins file.

Author: frasercrmck

libclc/CMakeLists.txt

@@ -489,17 +489,12 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
       set( MACRO_ARCH ${ARCH} )
     endif()
 
-    # Enable SPIR-V builtin function declarations, so they don't
-    # have to be explicity declared in the soruce.
-    list( APPEND build_flags -Xclang -fdeclare-spirv-builtins)
     set( LIBCLC_ARCH_OBJFILE_DIR "${LIBCLC_OBJFILE_DIR}/${arch_suffix}" )
     file( MAKE_DIRECTORY ${LIBCLC_ARCH_OBJFILE_DIR} )
 
     # OpenCL 3.0 extensions
     string(CONCAT CL_3_0_EXTENSIONS
       "-cl-ext="
-      "+cl_khr_fp64,"
-      "+cl_khr_fp16,"
       "+__opencl_c_3d_image_writes,"
       "+__opencl_c_images,"
       "+cl_khr_3d_image_writes")
@@ -573,6 +568,9 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
     if( BUILD_LIBSPIRV_${t} )
       set( spirv_build_flags ${build_flags} )
       list( APPEND spirv_build_flags
+        # Enable SPIR-V builtin function declarations, so they don't have to be
+        # explicity declared in the soruce.
+        -Xclang -fdeclare-spirv-builtins
         -I${CMAKE_CURRENT_SOURCE_DIR}/opencl/include
         -I${CMAKE_CURRENT_SOURCE_DIR}/libspirv/include/
       )