Generate Pods target in Mac OS X with the specified deployment target.

Fix #757

lib/cocoapods/platform.rb

@@ -116,5 +116,12 @@ module Pod
     def requires_legacy_ios_archs?
       (name == :ios) && deployment_target && (deployment_target < Version.new("4.3"))
     end
+
+    def deployment_target_setting_name
+      case @symbolic_name
+      when :ios then 'IPHONEOS_DEPLOYMENT_TARGET'
+      when :osx then 'MACOSX_DEPLOYMENT_TARGET'
+      end
+    end
   end
 end

lib/cocoapods/project.rb

@@ -63,9 +63,8 @@ module Pod
         settings['ARCHS'] = "armv6 armv7"
       end
 
-      if platform == :ios && platform.deployment_target
-        # TODO: add for osx as well
-        settings['IPHONEOS_DEPLOYMENT_TARGET'] = platform.deployment_target.to_s
+      if platform.deployment_target
+        settings[platform.deployment_target_setting_name] = platform.deployment_target.to_s
       end
 
       target.build_settings('Debug').merge!(settings)

spec/unit/project_spec.rb

@@ -90,4 +90,20 @@ describe 'Pod::Project' do
       target.build_settings('Release')["IPHONEOS_DEPLOYMENT_TARGET"].should == "4.0"
     end
   end
+
+  describe "concerning its :osx targets with a deployment target" do
+    before do
+      @project = Pod::Project.new
+    end
+
+    it "sets MACOSX_DEPLOYMENT_TARGET for both configurations" do
+      target = @project.add_pod_target('Pods', Pod::Platform.new(:osx))
+      target.build_settings('Debug')["MACOSX_DEPLOYMENT_TARGET"].should == "10.7"
+      target.build_settings('Release')["MACOSX_DEPLOYMENT_TARGET"].should == "10.7"
+
+      target = @project.add_pod_target('Pods', Pod::Platform.new(:osx, :deployment_target => "10.6"))
+      target.build_settings('Debug')["MACOSX_DEPLOYMENT_TARGET"].should == "10.6"
+      target.build_settings('Release')["MACOSX_DEPLOYMENT_TARGET"].should == "10.6"
+    end
+  end
 end