Add simple bp2build converter for java_test_host

Bug:281551424

Test: java_test_host_conversion_test.go and presubmits
Change-Id: I43ed26df0bacd63ef402de4d9733d19604005c35
diff --git a/java/base.go b/java/base.go
index 374138c..dd02ef8 100644
--- a/java/base.go
+++ b/java/base.go
@@ -2188,5 +2188,9 @@
 		if binary, ok := ctx.Module().(*Binary); ok {
 			javaBinaryHostBp2Build(ctx, binary)
 		}
+	case "java_test_host":
+		if testHost, ok := ctx.Module().(*TestHost); ok {
+			javaTestHostBp2Build(ctx, testHost)
+		}
 	}
 }