fixup! Tweaks to the build system

Make it possible to provide MOZ_PKG_MAC_DSSTORE, MOZ_PKG_MAC_BACKGROUND,
MOZ_PKG_MAC_ICON as environment variables. These files are not where the
build system expects it.

In our build system these files are in
tor-browser-build/projects/browser/Bundle-Data/BaseBrowser.dmg while the
build system expects it to be in browser/branding/tb-*.

For ./mach package to work properly when building for macos we need
these locations. Passing them as env vars is fine for building artifacts
in tbb.

toolkit/mozapps/installer/upload-files.mk

@@ -205,9 +205,9 @@ ifeq ($(MOZ_PKG_FORMAT),DMG)
 
   _ABS_MOZSRCDIR = $(shell cd $(MOZILLA_DIR) && pwd)
   PKG_DMG_SOURCE = $(MOZ_PKG_DIR)
-  MOZ_PKG_MAC_DSSTORE=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/dsstore
-  MOZ_PKG_MAC_BACKGROUND=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/background.png
-  MOZ_PKG_MAC_ICON=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/disk.icns
+  MOZ_PKG_MAC_DSSTORE?=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/dsstore
+  MOZ_PKG_MAC_BACKGROUND?=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/background.png
+  MOZ_PKG_MAC_ICON?=$(topsrcdir)/$(MOZ_BRANDING_DIRECTORY)/disk.icns
   INNER_MAKE_PACKAGE = \
     $(call py_action,make_dmg, \
         $(if $(MOZ_PKG_MAC_DSSTORE),--dsstore '$(MOZ_PKG_MAC_DSSTORE)') \