Missing -lz when using alternative to pkg-config for libz
Incorrect package-version reported by .pc
That's solely based on the lack of sync between the two platforms and also between the linker and the dependencies list. But that fix causes FTBFS due to unresolved symbols when linking libutil.dylib: "_GifErrorString", referenced from: _PrintGifError in qprintf.o because qprintf.o is now only in libgif not libutil. If libutil is (as name suggests) utility functions and (as the Makefile behaves on all platforms) not actually install libutil publicly, should it be static-only on all platforms?
Incorrect object files in shared libutil on darwin
Type-mismatch in libmpeg2/idct_mmx.c
I had already added that flag for test/unit/CMakeLists.txt (required for recent cppunit versions (see https://sourceforge.net/p/podofo/mailman/podofo-users/thread/1501515201.2032.64.camel%40litePDF.cz) via the more generic ADD_DEFINITIONS() function, so a more specific tool like the CXX_STANDARD variables seems better already.
fink needs to check linkage for /sw/src
fink-package-precedence has long handled this task. Maintainers place it manually in CompileScript (it also catches other wrong-tree classes of errors that require some information not easily determined from the .deb but trivial for the maintainer to know).