debian/rules: fixing file permissions in iceowl-extension

Some *.js, *.png and *.xul files inside iceowl-extension have execution
rights which we fix while building the package.
adding fix for skia on armel

Patch based on work from Mike Hommey
http://anonscm.debian.org/cgit/pkg-mozilla/iceweasel.git/commit/?id=8b0c5afbe7168840c345af96597fdd704be37036
fixing FTBFS on armel

Fixing build issue depended on wrong setup settings for armel.

Closes: #754633