[clang][lld][cmake] Simplify header dirs
We don't need to recompute the list LLVMConfig.cmake provides us.
When LLVM is being built, the list is two elements long: generated headers and headers from source.
When LLVM is already built,the list is one element long: the installed header directory containing both generated and hand-written sources.
Reviewed By: sebastian-ne
Differential Revision: https://reviews.llvm.org/D130553
GitOrigin-RevId: cc56a5022c94710d8393f1505f925494f7d2cc1c
1 file changed