GN: Fix build

GN is unhappy when a rule that consumes a file generated by
another rule doesn't depend directly on that rule.

This change also quiets output from invoking Dart to follow the
rule of GN builds that a successful build generates no output.

Review URL: https://codereview.chromium.org/2446473002 .

BUILD.gn

@@ -56,7 +56,8 @@ action("create_sdk") {
   deps = [
     "runtime/bin:dart",
     "utils/analysis_server",
-    "utils/compiler",
+    "utils/compiler:dart2js",
+    "utils/compiler:utils_wrapper",
     "utils/dartanalyzer:generate_dartanalyzer_snapshot",
     "utils/dartanalyzer:generate_summary_spec",
     "utils/dartanalyzer:generate_summary_strong",

tools/dart_for_gn.py

@@ -13,12 +13,23 @@
 import subprocess
 import sys
 
+def run_command(command):
+  try:
+    subprocess.check_output(command, stderr=subprocess.STDOUT)
+    return 0
+  except subprocess.CalledProcessError as e:
+    return ("Command failed: " + ' '.join(command) + "\n" +
+            "output: " + e.output)
+
 def main(argv):
   if len(argv) < 2:
     print "Requires path to Dart VM binary as first argument"
     return -1
-  command = argv[1:]
-  return subprocess.call(command)
+  result = run_command(argv[1:])
+  if result != 0:
+    print result
+    return -1
+  return 0
 
 if __name__ == '__main__':
     sys.exit(main(sys.argv))

utils/compiler/BUILD.gn

@@ -71,10 +71,3 @@ application_snapshot("utils_wrapper") {
   main_dart = "$root_gen_dir/utils_wrapper.dart"
   training_args = [ "--help" ]
 }
-
-group("compiler") {
-  deps = [
-    ":dart2js",
-    ":utils_wrapper",
-  ]
-}