build for en-US if no langs are specified

Change-Id: I21323d275f8381ecffa937563fccbc7bbb4b497e

solenv/gbuild/AllLangZip.mk

@@ -12,7 +12,7 @@
 # Handles creation of a bunch of zip files with content dependent on
 # language
 
-gb_AllLangZip_LANGS := $(gb_WITH_LANG)
+gb_AllLangZip_LANGS := $(if $(strip $(gb_WITH_LANG)),$(gb_WITH_LANG),en-US)
 
 $(dir $(call gb_AllLangZip_get_target,%)).dir :
 	$(if $(wildcard $(dir $@)),,mkdir -p $(dir $@))