Bug 1352982 - clobber OSX .app directory before rsyncing files in; r=ted

The .app directory for OSX builds is created piecemeal by several
commands in browser/app/Makefile.in, however it isn't normally cleaned
by a build. If a file is removed from the tree, it's possible that an
incremental build will still have a copy in the .app dir and get
packaged up in the final dmg. It's simple to just rm -rf this directory
beforehand.

MozReview-Commit-ID: 2Zr97o9dTn8

--HG--
extra : rebase_source : 2c9995991c58ee9724464514ec8285c31ab8d062

browser/app/Makefile.in

@@ -88,6 +88,7 @@ MAC_BUNDLE_VERSION = $(shell $(PYTHON) $(srcdir)/macversion.py --version=$(MOZ_A
 
 .PHONY: repackage
 tools repackage:: $(DIST)/bin/$(MOZ_APP_NAME)
+	rm -rf $(dist_dest)
 	$(MKDIR) -p $(dist_dest)/Contents/MacOS
 	$(MKDIR) -p $(dist_dest)/$(LPROJ)
 	rsync -a --exclude '*.in' $(srcdir)/macbuild/Contents $(dist_dest) --exclude English.lproj