when using Cocoa backend, force builtin jpeg and png libs (to avoid finding ones that might depend on X11).
when using Cocoa backend, force builtin jpeg and png libs (to avoid finding
ones that might depend on X11).


git-svn-id: ecbadac9c76e8cf640a0bca86f6bd796c98521e3@45758 27541ba8-7e3a-0410-8455-c3a389f83636

bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT,bbannier/ROOT