Clean up warnings

-Xlint:-options is not available on some earlier JDK 7s, but won't fail
if unsupported. It prevents the warning wanting bootclasspath specified
since target/source is 1.6.
diff --git a/compiler/src/test/golden/TestService.java.txt b/compiler/src/test/golden/TestService.java.txt
index 46f7116..a19f90c 100644
--- a/compiler/src/test/golden/TestService.java.txt
+++ b/compiler/src/test/golden/TestService.java.txt
@@ -90,6 +90,7 @@
           "grpc.testing.TestService", METHOD_HALF_DUPLEX_CALL);
     }
 
+    @SuppressWarnings("unchecked")
     private TestServiceServiceDescriptor(
         java.util.Map<java.lang.String, io.grpc.MethodDescriptor<?, ?>> methodMap) {
       unaryCall = (io.grpc.MethodDescriptor<io.grpc.testing.integration.Test.SimpleRequest,
diff --git a/compiler/src/test/golden/TestServiceNano.java.txt b/compiler/src/test/golden/TestServiceNano.java.txt
index 18f40fd..7e12113 100644
--- a/compiler/src/test/golden/TestServiceNano.java.txt
+++ b/compiler/src/test/golden/TestServiceNano.java.txt
@@ -152,6 +152,7 @@
           "grpc.testing.TestService", METHOD_HALF_DUPLEX_CALL);
     }
 
+    @SuppressWarnings("unchecked")
     private TestServiceServiceDescriptor(
         java.util.Map<java.lang.String, io.grpc.MethodDescriptor<?, ?>> methodMap) {
       unaryCall = (io.grpc.MethodDescriptor<io.grpc.testing.integration.Test.SimpleRequest,