[Command::Spec::Linter] Bug fix.

lib/cocoapods/command/spec.rb

@@ -296,7 +296,8 @@ module Pod
               # Skip Filelist that would otherwise be resolved from the working directory resulting
               # in a potentially very expensi operation
               next if pattern.is_a?(FileList)
-              if pattern.any? { |path| path.start_with?('/') }
+              invalid = pattern.is_a?(Array) ? pattern.any? { |path| path.start_with?('/') } : pattern.start_with?('/')
+              if invalid
                 messages << "Paths cannot start with a slash (#{accessor})"
                 break
               end