[CMake] Add the new clang features file to the distribution

clang-features-file was added to the install but not the distribution.
It's intended to communicate to build systems that a new feature and
associated flags are available, so should be added to the distribution.

Resolves rdar://72387110

Author: bnbarham

clang/cmake/caches/Apple-stage2.cmake

@@ -76,6 +76,7 @@ set(LLVM_DISTRIBUTION_COMPONENTS
   clang-resource-headers
   cxx-headers
   Remarks
+  clang-features-file
   ${LLVM_TOOLCHAIN_TOOLS}
   ${LLVM_TOOLCHAIN_UTILITIES}
   CACHE STRING "")