[build] Reduce dartdev bloat in the "runtime" target.

The dartdev JIT snapshot is not needed on not-IA32, where the AOT snapshot is used instead.

Change-Id: I8ee0f15dde1532e81c75013e4f2b1f56456ca146
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/508161
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>

BUILD.gn

@@ -51,7 +51,6 @@ group("runtime") {
     "samples/embedder:kernel",
     "samples/ffi/http:fake_http",
     "samples/ffi/httpIG:fake_httpIG",
-    "utils/dartdev",
     "utils/kernel-service",
   ]
 
@@ -71,6 +70,7 @@ group("runtime") {
   } else {
     deps += [
       "utils/dart_runtime_service_vm",
+      "utils/dartdev",
       "utils/dds",
       "utils/dtd",
       "utils/kernel-service:frontend_server",