Make test_options.timeout an int64

I forgot we supported integer properties, use an integer instead
of a string for test_options.timeout.

Test: m checkbuild
Change-Id: I22d3135b31ec93d15b530c430b9e9cda6dd3f416

java/robolectric.go

@@ -39,7 +39,7 @@ type robolectricProperties struct {
 
 	Test_options struct {
 		// Timeout in seconds when running the tests.
-		Timeout *string
+		Timeout *int64
 	}
 }