Q: gettext's Makefiles don't support VPATH.

A: It's some vendors' "make" which doesn't support VPATH.

   1) GNU make supports VPATH with both .c.o and %.o:%.c rules.

   2) Solaris make should not be used with VPATH at all, as it randomly
      changes Makefile variables.

   3) FreeBSD make does not support %.o:%.c rules at all. For the
      remaining .c.o rules VPATH is taken into account. For
      additional dependencies like "foo.o : bar.c" it is not.

   Since %.o:%.c rules are not portable, GNU package Makefiles
   shouldn't use them. Only .c.o rules. And then gettext's Makefiles
   should work with GNU make and with FreeBSD make. But Solaris make
   is not supportable with VPATH.