build: Only include traced service tests in android/standalone builds.

This should address the most recent chromium roll issue, e.g.:
https://chromium-review.googlesource.com/c/chromium/src/+/1526524

Change-Id: Ia75c3ebc95f487b55d9f3891eac18cb6f8dcb1a9
diff --git a/BUILD.gn b/BUILD.gn
index d941328..c54e571 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -113,7 +113,6 @@
     "gn:gtest_main",
     "src/base:unittests",
     "src/protozero:unittests",
-    "src/traced/service:unittests",
     "src/tracing:unittests",
   ]
 
@@ -125,6 +124,7 @@
       "src/traced/probes:unittests",
       "src/traced/probes/filesystem:unittests",
       "src/traced/probes/ftrace:unittests",
+      "src/traced/service:unittests",
       "tools/ftrace_proto_gen:unittests",
       "tools/sanitizers_unittests",
     ]