Update llvm manifest with build system changes

* platform/build must be checked out into build/make
* bootstrap.bash is obsolete
* prebuilts/ninja is obsolete
* external/golang-protobuf will be required

The use of build instead of build/make was causing my soong_ui change to
fail: https://android-review.googlesource.com/c/platform/build/soong/+/464643

Test: sync
Test: DIST_DIR=dist OUT_DIR=out python external/clang/build.py --build-name P4694484 --no-multi-stage --no-pgo-clang --no-debug-clang
Change-Id: I53b7a8eef9fda21285358052c0ec11423bf5dfb2
1 file changed
tree: 58e3169e24fe7643dfc49d052853061d9140182f
  1. default.xml