Something fishy about the current Makefiles

Whilst fooling around with GIN, I have repeatedly observed that doing
"make" in src/backend/access/gin, followed by "make install-bin" in
src/backend, fails to rebuild the postgres executable --- it just
installs the existing one.  A second execution of "make install-bin"
does notice that postgres is out of date and rebuilds it.  This
procedure for rebuilding after changing one or two .c files has always
worked for me before.  I can't avoid the suspicion that the recent
changes to make things more parallel-friendly broke something.
        regards, tom lane