[libspirv] Route SPIR-V pow* builtins through CLC (#18963)

These should have the potential to be more optimal for most targets, as
they emit vectorised codegen.

These were the last functions that tripped the bitwise conditional
parenthesis warning in libspirv, so that has been re-enabled.

Author: frasercrmck

libclc/CMakeLists.txt

@@ -575,8 +575,6 @@ foreach( t ${LIBCLC_TARGETS_TO_BUILD} )
       list( APPEND spirv_build_flags
         -I${CMAKE_CURRENT_SOURCE_DIR}/opencl/include
         -I${CMAKE_CURRENT_SOURCE_DIR}/libspirv/include/
-        # FIXME: Fix libspirv to not require disabling this noisy warning
-        -Wno-bitwise-conditional-parentheses
       )
 
       add_libclc_builtin_set(

libclc/libspirv/lib/generic/SOURCES

@@ -67,9 +67,6 @@ math/cbrt.cl
 math/ceil.cl
 math/clc_exp10.cl
 math/clc_fmod.cl
-math/clc_pow.cl
-math/clc_pown.cl
-math/clc_powr.cl
 math/clc_remainder.cl
 math/clc_remquo.cl
 math/clc_rootn.cl