Norbert Koch writes:
On some OSs you can't pass /usr/local, because the compiler issues a
warning about reordering include directories. This breaks configure.
Ah yes, I remember, later versions of gcc do that (I'm at 2.95.4).
On others (FreeBSD for example) it's necessary to add it, because
lot of goodies are found there. So the best way would be to make this
dependent on the OS at hand, but nobody has come to do this.
OK. It's not a big deal, just a slight surprise.