Bug 1455120 - Prefix output from automation tiers; r=mshal

We add a minimal Python script to run a process and prefix all its
output with a string. We change the automation tiers to evaluate all
make targets using this script.

MozReview-Commit-ID: 79g5KUd5ked

--HG--
extra : rebase_source : 63388a71b51e5abc05ca8bd48e180af72bf799e6

build/moz-automation.mk

@@ -76,7 +76,7 @@ AUTOMATION_EXTRA_CMDLINE-l10n-check = -j1
 # However, the target automation/buildsymbols will still be executed in this
 # case because it is a prerequisite of automation/upload.
 define automation_commands
-@+$(MAKE) $1 $(AUTOMATION_EXTRA_CMDLINE-$1)
+@+$(PYTHON) $(topsrcdir)/config/run-and-prefix.py $1 $(MAKE) $1 $(AUTOMATION_EXTRA_CMDLINE-$1)
 $(call BUILDSTATUS,TIER_FINISH $1)
 endef
 

config/run-and-prefix.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env python
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This script runs a process and prefixes its output with.
+# Usage: run-and-prefix.py prefix command arg0 argv1...
+
+from __future__ import absolute_import, print_function
+
+import os
+import subprocess
+import sys
+
+sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 0)
+sys.stderr = os.fdopen(sys.stderr.fileno(), 'w', 0)
+
+prefix = sys.argv[1]
+args = sys.argv[2:]
+
+p = subprocess.Popen(args, bufsize=0,
+                     stdout=subprocess.PIPE,
+                     stderr=subprocess.STDOUT,
+                     stdin=sys.stdin.fileno(),
+                     universal_newlines=True)
+
+while True:
+    data = p.stdout.readline()
+
+    if data == b'':
+        break
+
+    print('%s> %s' % (prefix, data), end=b'')
+
+sys.exit(p.wait())