Make cr build run goma_ctl.py ensure_start before building.

tools/cr/cr/base/host.py

Index: tools/cr/cr/base/host.py
diff --git a/tools/cr/cr/base/host.py b/tools/cr/cr/base/host.py
index c6e0ced86e6b3163e260b1da78f82bae2103b7f5..c6cb212980bc6badfbf86ed641d758916ecb85ad 100644
--- a/tools/cr/cr/base/host.py
+++ b/tools/cr/cr/base/host.py
@@ -41,8 +41,8 @@ class Host(cr.Plugin, cr.Plugin.Type):
         return host
 
   def _Execute(self, context, command,
-               shell=False, capture=False, ignore_dry_run=False,
-               return_status=False):
+               shell=False, capture=False, silent=False,
+               ignore_dry_run=False, return_status=False):
     """This is the only method that launches external programs.
 
     It is a thin wrapper around subprocess.Popen that handles cr specific
@@ -78,6 +78,8 @@ class Host(cr.Plugin, cr.Plugin.Type):
       out = None
       if capture:
         out = subprocess.PIPE
+      elif silent:
+        out = open(os.devnull, "w")
       try:
         p = subprocess.Popen(
             command, shell=shell,
@@ -97,6 +99,9 @@ class Host(cr.Plugin, cr.Plugin.Type):
         p.terminate()
         p.wait()
         exit(1)
+      finally:
+        if silent:
+          out.close()
       if return_status:
         return p.returncode
       if p.returncode != 0:
@@ -115,6 +120,10 @@ class Host(cr.Plugin, cr.Plugin.Type):
     return self._Execute(context, command, shell=False)
 
   @cr.Plugin.activemethod
+  def ExecuteSilently(self, context, *command):
+    return self._Execute(context, command, shell=False, silent=True)
+
+  @cr.Plugin.activemethod
   def CaptureShell(self, context, *command):
     return self._Execute(context, command,
                          shell=True, capture=True, ignore_dry_run=True)