https://sourceforge.net/p/xgalaga/bugs/11/
https://sourceforge.net/p/xgalaga/patches/4/
--- Makefile.in.orig	2008-03-05 15:58:16.000000000 -0600
+++ Makefile.in	2013-12-27 01:47:16.000000000 -0600
@@ -15,8 +15,7 @@
 bindir = $(exec_prefix)
 libdir = $(prefix)/lib
 infodir = $(prefix)/info
-#mandir = @mandir@
-mandir = /usr/share/man
+mandir = @mandir@
 creditsfile = @CREDITSFILE@
 distversion = 2.1.1.0
 
@@ -64,9 +62,8 @@
 	./mkinstalldirs $(DESTDIR)$(prefix)/levels
 	for i in levels/*.xgl; do $(INSTALL) $$i $(DESTDIR)$(prefix)/$$i ; done
 	for i in sounds/*.raw; do $(INSTALL) $$i $(DESTDIR)$(prefix)/$$i ; done
-	$(INSTALL) CREDITS $(DESTDIR)$(creditsfile)
-	$(INSTALL) xgalaga.6x.gz $(mandir)/man6/xgalaga.6x.gz
-	chmod 644 $(mandir)/man6/xgalaga.6x.gz
+	$(INSTALL) xgalaga.6x.gz $(DESTDIR)$(mandir)/man6/xgalaga.6x.gz
+	chmod 644 $(DESTDIR)$(mandir)/man6/xgalaga.6x.gz
 #	touch $(prefix)/scores
 #	chmod 666 $(prefix)/scores
 #       chown ${GAMEOWN}:${GAMEGRP} $(prefix)/scores