GN: Try to fix Linux build on bots

Review URL: https://codereview.chromium.org/2449213003 .

runtime/BUILD.gn

@@ -303,8 +303,8 @@ executable("libdart_dependency_helper") {
     "third_party/double-conversion/src:libdouble_conversion",
     "vm:libdart_lib",
     "vm:libdart_lib_nosnapshot",
-    "vm:libdart_platform",
     "vm:libdart_vm",
+    "vm:libdart_vm_nosnapshot",
   ]
   sources = [
     "vm/libdart_dependency_helper.cc",

utils/dartdevc/BUILD.gn

@@ -6,7 +6,11 @@ import("../invoke_dart.gni")
 
 application_snapshot("dartdevc") {
   main_dart = "../../pkg/dev_compiler/bin/dartdevc.dart"
-  training_args = [ "--help" ]
+  training_args = [
+    "--dart-sdk",
+    rebase_path("../../sdk"),
+    "--help"
+  ]
   inputs = exec_script("../../tools/list_dart_files.py",
                        [ rebase_path("../../pkg/dev_compiler/bin") ],
                        "list lines")