gyp-win-tool: Don't use shell=True on non-Windows hosts.

pylib/gyp/win_tool.py

 #!/usr/bin/env python
 
 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Utility functions for Windows builds.
 
 These functions are executed via gyp-win-tool when using the ninja generator.
 """
@@ skipping 101 matching lines @@
     """Filter diagnostic output from link that looks like:
     '   Creating library ui.dll.lib and object ui.dll.exp'
     This happens when there are exports from the dll or exe.
     """
     env = self._GetEnv(arch)
     if use_separate_mspdbsrv == 'True':
       self._UseSeparateMspdbsrv(env, args)
     if sys.platform == 'win32':
       args = list(args)  # *args is a tuple by default, which is read-only.
       args[0] = args[0].replace('/', '\\')
-    link = subprocess.Popen(args, shell=True, env=env,
+    # https://docs.python.org/2/library/subprocess.html:
+    # "On Unix with shell=True [...] if args is a sequence, the first item
+    # specifies the command string, and any additional items will be treated as
+    # additional arguments to the shell itself.  That is to say, Popen does the
+    # equivalent of:
+    #   Popen(['/bin/sh', '-c', args[0], args[1], ...])"
+    # For that reason, since going through the shell doesn't seem necessary on
+    # non-Windows don't do that there.
+    link = subprocess.Popen(args, shell=sys.platform == 'win32', env=env,
                             stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
     out, _ = link.communicate()
     for line in out.splitlines():
       if (not line.startswith('   Creating library ') and
           not line.startswith('Generating code') and
           not line.startswith('Finished generating code')):
         print line
     return link.returncode
 
   def ExecLinkWithManifests(self, arch, embed_manifest, out, ldcmd, resname,
@@ skipping 172 matching lines @@
     project_dir = os.path.relpath(project_dir, BASE_DIR)
     selected_files = selected_files.split(';')
     ninja_targets = [os.path.join(project_dir, filename) + '^^'
         for filename in selected_files]
     cmd = ['ninja.exe']
     cmd.extend(ninja_targets)
     return subprocess.call(cmd, shell=True, cwd=BASE_DIR)
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))