Bug 1574115 - Follow-up: Fix paths to macOS filesystem tools. r=jorgk

For failing macOS L10n repacks.

mail/config/mozconfigs/macosx64/l10n-mozconfig

@@ -3,7 +3,7 @@
 if test `uname -s` = "Linux"; then
   # We need to indicate the target for cross builds
   ac_add_options --target=x86_64-apple-darwin
-  export MKFSHFS=$topsrcdir/hfsplus-tools/newfs_hfs
-  export DMG_TOOL=$topsrcdir/dmg/dmg
-  export HFS_TOOL=$topsrcdir/dmg/hfsplus
+  export MKFSHFS=$MOZ_FETCHES_DIR/hfsplus-tools/newfs_hfs
+  export DMG_TOOL=$MOZ_FETCHES_DIR/dmg/dmg
+  export HFS_TOOL=$MOZ_FETCHES_DIR/dmg/hfsplus
 fi