Compile appcompat with Java 7

Change-Id: I09aafe9782d966c3f98f1be49562853fb37d2604
diff --git a/v7/appcompat/build.gradle b/v7/appcompat/build.gradle
index c1f91ec..5ad5189 100644
--- a/v7/appcompat/build.gradle
+++ b/v7/appcompat/build.gradle
@@ -23,6 +23,11 @@
         androidTest.java.srcDir 'tests/src'
     }
 
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_7
+        targetCompatibility JavaVersion.VERSION_1_7
+    }
+
     lintOptions {
         // TODO: fix errors and reenable.
         abortOnError false