Rework how MB and GN handle concurrent links.

tools/mb/mb.py

 #!/usr/bin/env python
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """MB - the Meta-Build wrapper around GYP and GN
 
 MB is a wrapper script for GYP and GN that can be used to generate build files
 for sets of canned configurations and analyze them.
 """
@@ skipping 1109 matching lines @@
     # This is a terrible hack to work around the fact that
     # //tools/clang/scripts/update.py is invoked by GYP and GN but
     # currently relies on an environment variable to figure out
     # what revision to embed in the command line #defines.
     # For GN, we've made this work via a gn arg that will cause update.py
     # to get an additional command line arg, but getting that to work
     # via GYP_DEFINES has proven difficult, so we rewrite the GYP_DEFINES
     # to get rid of the arg and add the old var in, instead.
     # See crbug.com/582737 for more on this. This can hopefully all
     # go away with GYP.
-    if 'llvm_force_head_revision=1' in gyp_defines:
+    m = re.search('llvm_force_head_revision=1\s*', gyp_defines)
+    if m:
       env['LLVM_FORCE_HEAD_REVISION'] = '1'
-      gyp_defines = gyp_defines.replace('llvm_force_head_revision=1', '')
+      gyp_defines = gyp_defines.replace(m.group(0), '')
+
+    # This is another terrible hack to work around the fact that
+    # GYP sets the link concurrency to use via the GYP_LINK_CONCURRENCY
+    # environment variable, and not via a proper GYP_DEFINE. See
+    # crbug.com/611491 for more on this.
+    m = re.search('gyp_link_concurrency=(\d+)(\s*)', gyp_defines)
+    if m:
+      env['GYP_LINK_CONCURRENCY'] = m.group(1)
+      gyp_defines = gyp_defines.replace(m.group(0), '')
 
     env['GYP_GENERATORS'] = 'ninja'
     if 'GYP_CHROMIUM_NO_ACTION' in env:
       del env['GYP_CHROMIUM_NO_ACTION']
     if 'GYP_CROSSCOMPILE' in env:
       del env['GYP_CROSSCOMPILE']
     env['GYP_DEFINES'] = gyp_defines
     if vals['gyp_crosscompile']:
       env['GYP_CROSSCOMPILE'] = '1'
     return cmd, env
@@ skipping 173 matching lines @@
       env_prefix = ''
       env_quoter = pipes.quote
       shell_quoter = pipes.quote
 
     def print_env(var):
       if env and var in env:
         self.Print('%s%s=%s' % (env_prefix, var, env_quoter(env[var])))
 
     print_env('GYP_CROSSCOMPILE')
     print_env('GYP_DEFINES')
+    print_env('GYP_LINK_CONCURRENCY')
+    print_env('LLVM_FORCE_HEAD_REVISION')
 
     if cmd[0] == self.executable:
       cmd = ['python'] + cmd[1:]
     self.Print(*[shell_quoter(arg) for arg in cmd])
 
   def PrintJSON(self, obj):
     self.Print(json.dumps(obj, indent=2, sort_keys=True))
 
   def GNTargetName(self, target):
     return target
@@ skipping 133 matching lines @@
   # Then check to see if the arg contains any metacharacters other than
   # double quotes; if it does, quote everything (including the double
   # quotes) for safety.
   if any(a in UNSAFE_FOR_CMD for a in arg):
     arg = ''.join('^' + a if a in ALL_META_CHARS else a for a in arg)
   return arg
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))