Remove unused and obsolete build flag (#2179)

Stack from [ghstack](https://github.com/ezyang/ghstack) (oldest at
bottom):
* __->__ #2179

Author: guangyey

cmake/BuildFlags.cmake

@@ -100,8 +100,6 @@ if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID STREQUAL "MSVC"
     set(SYCL_KERNEL_OPTIONS ${SYCL_KERNEL_OPTIONS} -gline-tables-only -O2)
   endif()
 
-  set(SYCL_KERNEL_OPTIONS ${SYCL_KERNEL_OPTIONS} -D__INTEL_LLVM_COMPILER_VERSION=${__INTEL_LLVM_COMPILER})
-
   CHECK_SYCL_FLAG("-fsycl-fp64-conv-emu" SUPPORTS_FP64_CONV_EMU)
   if(SUPPORTS_FP64_CONV_EMU)
     set(SYCL_KERNEL_OPTIONS ${SYCL_KERNEL_OPTIONS} -fsycl-fp64-conv-emu)