xcode: work on schemes, preparing for dependencies in the workspace
xcode: prevent duplicate file references from being added
breaking change: refactoring BuildCache and command execution
continue refactoring; cleaning up build cache; mostly working again
more refactoring and cleanup; xcworkspaces are generated again
msbuild: Fix solution generation after refactor
Fix makefile generation after refactor
adding safeguards for invalid returns
refactoring, cleanup and bug fixes

BuildCache work to organize dependencies.
Fixed an issue where we were relying on fuzzy string matching for product names
Fixed dependency ordering issue for products

- Needs work on isolating one call per buildfile next...
Improved command execution; gmake now working correctly
update msbuild generator
update xcode generator; also add GCC_WARN_ABOUT_RETURN_TYPE