Use custom target to create symlinks for Vc/VecCore headers
Use custom target to create symlinks for Vc/VecCore headers

Using execute_process() fails to create the symlink on a clean
build directory, because ${CMAKE_BINARY_DIR}/include does not
exist yet at configuration time.

root-mirror/root,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,olifre/root,karies/root,zzxuanyuan/root,olifre/root,karies/root,olifre/root,olifre/root,olifre/root,olifre/root,karies/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,root-mirror/root,karies/root,root-mirror/root,olifre/root,karies/root,karies/root,root-mirror/root,karies/root,root-mirror/root,root-mirror/root,olifre/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,zzxuanyuan/root,olifre/root,olifre/root,root-mirror/root,karies/root,root-mirror/root,zzxuanyuan/root,zzxuanyuan/root,zzxuanyuan/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root