ART: Restrict dex2oat watchdog dumping to host

Follow-up to commit cd607315e1e75feb3d1fab503d79586f26213970.

Bug: 62337922
Test: m test-art-host
Change-Id: I1d84bf2d7868cf6e3524da90cff2439e230264db
diff --git a/dex2oat/dex2oat.cc b/dex2oat/dex2oat.cc
index 80d5a9c..dcdf3bc 100644
--- a/dex2oat/dex2oat.cc
+++ b/dex2oat/dex2oat.cc
@@ -478,7 +478,10 @@
                                        android::base::LogId::DEFAULT,
                                        LogSeverity::FATAL,
                                        message.c_str());
-    if (Runtime::Current() != nullptr) {
+    // If we're on the host, try to dump all threads to get a sense of what's going on. This is
+    // restricted to the host as the dump may itself go bad.
+    // TODO: Use a double watchdog timeout, so we can enable this on-device.
+    if (!kIsTargetBuild && Runtime::Current() != nullptr) {
       Runtime::Current()->AttachCurrentThread("Watchdog thread attached for dumping",
                                               true,
                                               nullptr,