Create fat builds of static, dynamic & framework libraries if both iOS
and simulator versions have been created from separate manual Xcode builds.
Refactor scripts for creating fat libraries to reuse across projects.
Add MVK_BUILT_PROD_DIR to replace use of BUILT_PRODUCTS_DIR in most scripts
to allow flexibility across per-platform compilation.
Add ExternalDependencies (Debug) scheme to ExternalDependencies Xcode project.
Add --debug option to fetchDependencies script.
Support Release, Debug & Latest directories in External/build directory.
Enable DEPLOYMENT_POSTPROCESSING build setting when compiling
SPIRV-Tools to avoid warning spam when building dylibs.
Disable visibility warnings when building MoltenVKShaderConverter
in Release mode from external libraries built in Debug mode.
Always use -Xlinker -w option when creating dylibs to disable visibility warnings.
Refactor build scripts.
Update paths to MoltenVKGLSLToSPIRVConverter framework in demos.
Fix rare build race condition on MoltenVKShaderConverter link to MoltenVK.
