When MacOS support was updated (JDK-8075400, JDK-8267545) the entire contents of $(LFLAGS) were added to LFLAGS_JSIG and SA_LFLAGS on Darwin only.

This was done to add the -mmacosx-version-min argument but it also duplicates a whole bunch of other linker flags already added locally in these Makefiles.

As LFLAGS includes EXTRA_CFLAGS, this also means it adds a number of C++ flags to a C build, retaining the issue fixed for other platforms by JDK-8374917.

We can add the Mac specific flags to their own variable, MAC_FLAGS, in gcc.make and then only add the flags we actually need in saproc.make and jsig.make