Fix mangle filter

Right now the mangler will miss libraries that have the main pod name within their name. For example, if you're mangling for `A.podspec` which depends on `AFNetworking`, the `AFNetworking` lib will not be mangled because it contains the letter `A`.
Maybe `File.basename(file) == "libPods-#{pod_name}.a"`. `Dir.glob` returns whatever portion of the path is used in the glob.