Bug 1159371 - Allow compiling sub-directories with --disable-compile-environment. r=glandium

Without this, invoking Make in a sub-directory will fail with an error
that libs:: cannot find target `target'.

Without this patch, the Fennec Gradle and IDE build integration fails
compiling its custom targets in mobile/android/base and
mobile/android/base/locales.

--HG--
extra : rebase_source : a105072aee28e4f7693958a175d1d8ce3188b5f4
extra : source : 3232d253cf909e38da318c3ed3c04e7b5fc6a94f

config/recurse.mk

@@ -124,7 +124,9 @@ endef
 $(foreach subtier,$(filter-out compile,$(TIERS)),$(eval $(call CREATE_SUBTIER_TRAVERSAL_RULE,$(subtier))))
 
 ifndef TOPLEVEL_BUILD
+ifdef COMPILE_ENVIRONMENT
 libs:: target host
+endif # COMPILE_ENVIRONMENT
 endif
 
 endif # ifeq ($(NO_RECURSE_MAKELEVEL),$(MAKELEVEL))