Avoid error from mkdir if no languages are to be installed

mkinstalldirs used to handle no arguments, but mkdir doesn't.

Also remove the .SILENT setting, that was previously removed from
Makefile.global as well.

src/nls-global.mk

-# $PostgreSQL: pgsql/src/nls-global.mk,v 1.21 2009/08/26 22:24:42 petere Exp $
+# $PostgreSQL: pgsql/src/nls-global.mk,v 1.22 2010/05/13 14:35:28 petere Exp $
 
 # Common rules for Native Language Support (NLS)
 #
@@ -72,10 +72,10 @@ ifneq (,$(LANGUAGES))
 endif
 
 installdirs-po:
-	$(MKDIR_P) $(foreach lang, $(LANGUAGES), '$(DESTDIR)$(localedir)'/$(lang)/LC_MESSAGES)
+	$(if $(LANGUAGES),$(MKDIR_P) $(foreach lang, $(LANGUAGES), '$(DESTDIR)$(localedir)'/$(lang)/LC_MESSAGES),:)
 
 uninstall-po:
-	rm -f $(foreach lang, $(LANGUAGES), '$(DESTDIR)$(localedir)'/$(lang)/LC_MESSAGES/$(CATALOG_NAME)$(SO_MAJOR_VERSION)-$(MAJORVERSION).mo)
+	$(if $(LANGUAGES),rm -f $(foreach lang, $(LANGUAGES), '$(DESTDIR)$(localedir)'/$(lang)/LC_MESSAGES/$(CATALOG_NAME)$(SO_MAJOR_VERSION)-$(MAJORVERSION).mo),:)
 
 
 clean-po:
@@ -130,4 +130,3 @@ maintainer-check: maintainer-check-po
 
 .PHONY: all-po install-po installdirs-po uninstall-po clean-po \
         maintainer-check-po init-po update-po
-.SILENT: installdirs-po