[xcconfig] Only quote the path to the -isystem option.

Conflicts:
	lib/cocoapods/generator/xcconfig/aggregate_xcconfig.rb
	spec/unit/generator/xcconfig/aggregate_xcconfig_spec.rb

lib/cocoapods/generator/xcconfig/aggregate_xcconfig.rb

@@ -44,13 +44,13 @@ module Pod
       # @return [Xcodeproj::Config]
       #
       def generate
-      	header_search_path_flags = target.sandbox.public_headers.search_paths.map {|path| '-isystem'+path}
+        header_search_path_flags = target.sandbox.public_headers.search_paths
         @xcconfig = Xcodeproj::Config.new({
           'OTHER_LDFLAGS' => XCConfigHelper.default_ld_flags(target),
           'HEADER_SEARCH_PATHS' => XCConfigHelper.quote(target.sandbox.public_headers.search_paths),
           'PODS_ROOT' => target.relative_pods_root,
           'GCC_PREPROCESSOR_DEFINITIONS' => '$(inherited) COCOAPODS=1',
-          'OTHER_CFLAGS' => '$(inherited) ' + XCConfigHelper.quote(header_search_path_flags)
+          'OTHER_CFLAGS' => '$(inherited) ' + XCConfigHelper.quote(header_search_path_flags, '-isystem')
         })
 
         target.pod_targets.each do |pod_target|

lib/cocoapods/generator/xcconfig/xcconfig_helper.rb

@@ -13,10 +13,13 @@ module Pod
         # @param  [Array<String>] strings
         #         a list of strings.
         #
+        # @param  [String] optional prefix, such as a flag or option.
+        #
         # @return [String] the resulting string.
         #
-        def self.quote(strings)
-          strings.sort.map { |s| %W|"#{s}"| }.join(" ")
+        def self.quote(strings, prefix = nil)
+          prefix = "#{prefix} " if prefix
+          strings.sort.map { |s| %W|#{prefix}"#{s}"| }.join(" ")
         end
 
         # @return [String] the default linker flags. `-ObjC` is always included

spec/unit/generator/xcconfig/aggregate_xcconfig_spec.rb

@@ -61,7 +61,7 @@ module Pod
         end
 
         it 'adds the sandbox public headers search paths to the xcconfig, with quotes, as system headers' do
-          expected = "$(inherited) \"-isystem#{config.sandbox.public_headers.search_paths.join('" -isystem"')}\""
+          expected = "$(inherited) -isystem \"#{config.sandbox.public_headers.search_paths.join('" -isystem "')}\""
           @xcconfig.to_hash['OTHER_CFLAGS'].should == expected
         end
 

spec/unit/generator/xcconfig/xcconfig_helper_spec.rb

@@ -37,6 +37,11 @@ module Pod
             result = @sut.quote(['string1', 'string2'])
             result.should == '"string1" "string2"'
           end
+
+          it "inserts an optional string and then the normal quoted string" do
+            result = @sut.quote(['string1', 'string2'], '-isystem')
+            result.should == '-isystem "string1" -isystem "string2"'
+          end
         end
 
         #---------------------------------------------------------------------#