Set compatible_with=appengine on targets depended on by App Engine apps or by the App Engine runtime itself.

This CL has minimal[*] immediate impact on the targets, but it has two consequences moving forward:
- When [] moves to Java 8, compatible_with=appengine targets will remain on Java 7. (If this target is a non-java_* target, you can ignore this bullet.)
- compatible_with=appengine targets can depend only on other compatible_with=appengine targets. (Fortunately, most common libraries will be compatible_with=appengine: []
This CL is one of thousands in a migration on the critical path for Java 8, so please respond promptly, and, if you are the wrong reviewer, please reassign the CL.

[*] It does mean that your target will go back to being compiled to Java 7 bytecode after its recent switch to Java 8 ([]If your target compiles the same files as another non-compatible_with=appengine target, this CL may break one_definition_test targets.

More information:
[]
Tested:
[] build --nobuild

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=129660908

java/google/registry/dns/writer/clouddns/BUILD

@@ -8,6 +8,7 @@ licenses(["notice"])  # Apache 2.0
 java_library(
     name = "clouddns",
     srcs = glob(["*.java"]),
+    compatible_with = ["//buildenv/target:appengine"],
     deps = [
         "//apiserving/discoverydata/cloud/dns:cloud_dns_v2beta1_versioned",
         "//java/com/google/api/client/googleapis/json",