Add support for the GYP_CROSSCOMPILE env var to MB.

tools/mb/mb.py

Index: tools/mb/mb.py
diff --git a/tools/mb/mb.py b/tools/mb/mb.py
index f2af24c332c12d5f667485a2e5afc4b0aac184e9..f30fc3a1240742a9b01338575205fee309362fb0 100755
--- a/tools/mb/mb.py
+++ b/tools/mb/mb.py
@@ -147,6 +147,8 @@ class MetaBuildWrapper(object):
     if vals['type'] == 'gn':
       cmd = self.GNCmd('gen', '<path>', vals['gn_args'])
     elif vals['type'] == 'gyp':
+      if vals['gyp_crosscompile']:
+        self.Print('GYP_CROSSCOMPILE=1')
       cmd = self.GYPCmd('<path>', vals['gyp_defines'], vals['gyp_config'])
     else:
       raise MBErr('Unknown meta-build type "%s"' % vals['type'])
@@ -289,6 +291,7 @@ class MetaBuildWrapper(object):
       'gn_args': [],
       'gyp_config': [],
       'gyp_defines': [],
+      'gyp_crosscompile': False,
     }
 
     visited = []
@@ -314,6 +317,8 @@ class MetaBuildWrapper(object):
           vals['gn_args'] = mixin_vals['gn_args']
       if 'gyp_config' in mixin_vals:
         vals['gyp_config'] = mixin_vals['gyp_config']
+      if 'gyp_crosscompile' in mixin_vals:
+        vals['gyp_crosscompile'] = mixin_vals['gyp_crosscompile']
       if 'gyp_defines' in mixin_vals:
         if vals['gyp_defines']:
           vals['gyp_defines'] += ' ' + mixin_vals['gyp_defines']
@@ -426,7 +431,13 @@ class MetaBuildWrapper(object):
                   'GYP configuration specified in the config (%s), and '
                   'it does not.' % (gyp_config, vals['gyp_config']))
     cmd = self.GYPCmd(output_dir, vals['gyp_defines'], config=gyp_config)
-    ret, _, _ = self.Run(cmd)
+    env = None
+    if vals['gyp_crosscompile']:
+      if self.args.verbose:
+        self.Print('Setting GYP_CROSSCOMPILE=1 in the environment')
+      env = os.environ.copy()
+      env['GYP_CROSSCOMPILE'] = '1'
+    ret, _, _ = self.Run(cmd, env=env)
     return ret
 
   def RunGYPAnalyze(self, vals):
@@ -752,13 +763,13 @@ class MetaBuildWrapper(object):
     # This function largely exists so it can be overridden for testing.
     print(*args, **kwargs)
 
-  def Run(self, cmd):
+  def Run(self, cmd, env=None):
     # This function largely exists so it can be overridden for testing.
     if self.args.dryrun or self.args.verbose:
       self.PrintCmd(cmd)
     if self.args.dryrun:
       return 0, '', ''
-    ret, out, err = self.Call(cmd)
+    ret, out, err = self.Call(cmd, env=env)
     if self.args.verbose:
       if out:
         self.Print(out, end='')
@@ -766,9 +777,10 @@ class MetaBuildWrapper(object):
         self.Print(err, end='', file=sys.stderr)
     return ret, out, err
 
-  def Call(self, cmd):
+  def Call(self, cmd, env=None):
     p = subprocess.Popen(cmd, shell=False, cwd=self.chromium_src_dir,
-                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE,
+                         env=env)
     out, err = p.communicate()
     return p.returncode, out, err