[libclc] Build for OpenCL 3.0 (llvm#135733)

This PR is modified cherry-pick of
intel/llvm@cba338e5fb1c
This PR sets OpenCL language version to be the same, which is 3.0,
for every target and device, in order to unify the build process.
Target should define supported extensions and features via
setSupportedOpenCLOpts API.

llvm-diff shows one change to amdgcn--amdhsa.bc:
* ctz symbols are added since they are now enabled for amdgcn.

Author: wenju-he

libclc/CMakeLists.txt

@@ -411,6 +411,9 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
     set( LIBCLC_ARCH_OBJFILE_DIR "${LIBCLC_OBJFILE_DIR}/${arch_suffix}" )
     file( MAKE_DIRECTORY ${LIBCLC_ARCH_OBJFILE_DIR} )
 
+    # Build for OpenCL 3.0 independently of the target or device.
+    list( APPEND build_flags -cl-std=CL3.0 )
+
     string( TOUPPER "CLC_${MACRO_ARCH}" CLC_TARGET_DEFINE )
 
     list( APPEND build_flags