Bug 835164 Unbreak Seamonkey and Xulrunner mac universal builds after bug 834228 r=Callek.

build/macosx/universal/flight.mk

@@ -28,7 +28,7 @@ postflight_all:
 	ln -s $(call core_abspath,$(DIST_UNI)) $(DIST_ARCH_2)/universal
 # Stage a package for buildsymbols to be happy. Doing so in OBJDIR_ARCH_1
 # actually does a universal staging with both OBJDIR_ARCH_1 and OBJDIR_ARCH_2.
-	$(MAKE) -C $(OBJDIR_ARCH_1)/$(INSTALLER_DIR) \
+	$(MAKE) -C $(OBJDIR_ARCH_1)/$(MOZ_BUILD_APP)/installer \
 	   PKG_SKIP_STRIP=1 stage-package
 ifdef ENABLE_TESTS
 # Now, repeat the process for the test package.