[flang-commits] [flang] [flang] Fix finding system install of LLVM/Clang/MLIR in standalone builds (PR #120914)

[Leandro Lupori via flang-commits]

luporl wrote:

This broke flang-aarch64-out-of-tree: https://lab.llvm.org/buildbot/#/builders/53/builds/10501

https://github.com/llvm/llvm-project/pull/120914