- Add googletest and spirv-tools local builds only if their CMake targets
are not already configured.
- Add local spirv-headers as an include directory only if the associated
CMake directory does not already point to a directory.
Change-Id: I53ebb0d8fdf7703e8219000b78c75c30859c91a4
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/24020
Reviewed-by: dan sinclair <dsinclair@google.com>