[CMake] We need to explicitly add llvm-config before clang so that LLVM_BUILD_EXTERNAL_COMPILER_RT can depend on llvm-config.

This patch is a required stepping stone to fix PR14109.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249202 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed