Makefile: tweak sed invocation

With GNU sed, the r command doesn't care if a space separates it and
the filename it reads from.

With SunOS sed, the space is required.

Signed-off-by: Alejandro R. Sedeño <asedeno@mit.edu>
Reviewed-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -2086,7 +2086,7 @@ $(SCRIPT_PERL_GEN): % : %.perl GIT-PERL-DEFINES GIT-PERL-HEADER GIT-VERSION-FILE
 	$(QUIET_GEN)$(RM) $@ $@+ && \
 	sed -e '1{' \
 	    -e '	s|#!.*perl|#!$(PERL_PATH_SQ)|' \
-	    -e '	rGIT-PERL-HEADER' \
+	    -e '	r GIT-PERL-HEADER' \
 	    -e '	G' \
 	    -e '}' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \