Support the setting of file-specific compiler flags when adding source files to the project.

We'll need this to support #8.

lib/cocoapods/xcode/project.rb

@@ -50,14 +50,15 @@ module Pod
         end.compact
       end
 
-      def add_source_file(file)
+      def add_source_file(file, compiler_flags = nil)
         file_ref_uuid = add_file_reference(file, 'SOURCE_ROOT')
         add_file_to_group(file_ref_uuid, 'Pods')
         if file.extname == '.h'
           build_file_uuid = add_build_file(file_ref_uuid, "settings" => { "ATTRIBUTES" => ["Public"] })
           add_file_to_list('PBXHeadersBuildPhase', build_file_uuid)
         else
-          build_file_uuid = add_build_file(file_ref_uuid)
+          extra = compiler_flags ? {"settings" => { "COMPILER_FLAGS" => compiler_flags }} : {}
+          build_file_uuid = add_build_file(file_ref_uuid, extra)
           add_file_to_list('PBXSourcesBuildPhase', build_file_uuid)
         end
         file_ref_uuid

spec/unit/xcode/project_spec.rb

@@ -38,6 +38,19 @@ describe "Pod::Xcode::Project" do
     end
   end
 
+  it "adds custom compiler flags to the PBXBuildFile object if specified" do
+    build_file_uuids = []
+    %w{ m mm c cpp }.each do |ext|
+      path = Pathname.new("path/to/file.#{ext}")
+      file_ref_uuid = @project.add_source_file(path, '-fno-obj-arc')
+      @project.find_object({
+        'isa' => 'PBXBuildFile',
+        'fileRef' => file_ref_uuid,
+        'settings' => {'COMPILER_FLAGS' => '-fno-obj-arc' }
+      }).should.not == nil
+    end
+  end
+
   it "adds a `h' file as a build file and adds it to the `headers build' phase list" do
     path = Pathname.new("path/to/file.h")
     file_ref_uuid = @project.add_source_file(path)