message: Fixed SPIRV-Headers submodule path
diff: path = External/SPIRV-Tools
  url = https://github.com/DiligentGraphics/SPIRV-Tools.git
  [submodule "external/SPIRV-Headers"]
  - path = external/SPIRV-Headers
  + path = External/SPIRV-Headers
  url = https://github.com/DiligentGraphics/SPIRV-Headers.git
  