The source project of this merge request has been removed.
build_spec: remove glslang lock on mesa_master and lock spirvtools for stable builds
The bug affecting glslang and shaderc has been fixed (https://github.com/KhronosGroup/glslang/pull/1434), so this moves glslang to master branch again, and locks spirvtools to a sha that will build with the older glslang for stable builds