For some reason, the alloca module uses Autoconf's stock LIBOBJ
machinery and things explode if AC_CONFIG_LIBOBJ_DIR is not set
correctly, because the Gnulib macros sure don't.
Add such a call to the included m4 fragment to fix things up.
The amount of magic and poor documentation around this feature is
astounding.
], [dnl M4 code follows
AC_SUBST([GLSRC], [lib])
+AC_CONFIG_LIBOBJ_DIR([lib])
AC_DEFUN_ONCE([DX_GLSYM_PREFIX], [dnl
AC_REQUIRE([DX_EXPORTED_SH])