usr.bin/gh-bc: fix Makefile for WITHOUT_NLS_CATALOGS case

Some macro definitions had been moved into a Makefile section
that depends on MK_NLS_CATALOGS != "no", leading to LTO and the
installation of tests being disabled in the WITHOUT_NLS_CATALOGS
case.

Reported by: Yuri <yuri@aetern.org>

(cherry picked from commit 382af2f8d7bf576ff583543737e1134701ccc63d)