[all-commits] [llvm/llvm-project] 18a18b: Fix standalone clang builds after fb80b6b2d58.

[Nico Weber via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 18a18b20017d8d6d907ce409f0dc9585cec8bf72
      https://github.com/llvm/llvm-project/commit/18a18b20017d8d6d907ce409f0dc9585cec8bf72
  Author: Nico Weber <thakis at chromium.org>
  Date:   2020-04-03 (Fri, 03 Apr 2020)

  Changed paths:
    M llvm/cmake/modules/AddLLVM.cmake

  Log Message:
  -----------
  Fix standalone clang builds after fb80b6b2d58.

When clang is built against a prebuilt LLVM, LLVM_SOURCE_DIR is
empty, which due to a cmake quirk caused list lengths to get out
of sync. Add a workaround.