patch 8.1.1255: building desktop files fails on FreeBSD

Problem:    Building desktop files fails on FreeBSD. (Adam Weinberger)
Solution:   Avoid using non-portable construct in Makefile. (closes #4332)
diff --git a/src/po/Makefile b/src/po/Makefile
index 7c03fe4..cc56b83 100644
--- a/src/po/Makefile
+++ b/src/po/Makefile
@@ -165,9 +165,13 @@
 		po/gvim.desktop.in po/vim.desktop.in
 	mv -f ../$(PACKAGE).po $(PACKAGE).pot
 
-%.desktop: %.desktop.in $(POFILES)
+vim.desktop: vim.desktop.in $(POFILES)
 	@echo $(LANGUAGES) | tr " " "\n" |sed -e '/\./d' | sort > LINGUAS
-	$(MSGFMT) --desktop -d . --template $< -o $@
+	$(MSGFMT) --desktop -d . --template vim.desktop.in -o vim.desktop
+
+gvim.desktop: gvim.desktop.in $(POFILES)
+	@echo $(LANGUAGES) | tr " " "\n" |sed -e '/\./d' | sort > LINGUAS
+	$(MSGFMT) --desktop -d . --template gvim.desktop.in -o gvim.desktop
 
 update-po: $(LANGUAGES)