Modules with source files with identical basenames, but different paths, fail to link

[markfinal]

The problem is illustrated (pre-fix) by the DuplicateSourceFilenameTest. Two source files are called test.c, but are in different folders, source/A and source/B. The default output path is to collapse any subdirectory path, and just use the basename in the module's build configuration folder. This means both source files are written to the same location, and the linker will either indicate one symbol is missing, or that there is a duplicate symbol.

VisualStudio and Xcode projects also need to do something clever.