GN: Allow setting the path to Python

tools/gn/switches.cc

 // Copyright 2014 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.
 
 #include "tools/gn/switches.h"
 
 namespace switches {
 
 const char kArgs[] = "args";
 const char kArgs_HelpShort[] =
@@ skipping 85 matching lines @@
 const char kMarkdown_HelpShort[] =
     "--markdown: Write help output in the Markdown format.";
 const char kMarkdown_Help[] =
     "--markdown: Write help output in the Markdown format.\n";
 
 const char kNoColor[] = "nocolor";
 const char kNoColor_HelpShort[] =
     "--nocolor: Force non-colored output.";
 const char kNoColor_Help[] = COLOR_HELP_LONG;
 
+const char kScriptExecutable[] = "script-executable";
+const char kScriptExecutable_HelpShort[] =
+    "--script-executable: Set the executable used to execute scripts.";
+const char kScriptExecutable_Help[] =
+    "--script-executable: Set the executable used to execute scripts.\n"
+    "\n"
+    "  By default GN uses Python to execute scripts in action targets and\n"

[brettw, 2016/05/13 17:03:44]

Can you change this to:

By default GN searches the PATH for Python to execute scripts in action targets
and exec_script calls. This flag allows the specification of a specific Python
executable or potentially a different language interpreter.

[Petr Hosek, 2016/05/13 18:13:47]

Done.

+    "  exec_scripts function invocations. This flag allows using a custom\n"
+    "  executable.\n";
+
 const char kQuiet[] = "q";
 const char kQuiet_HelpShort[] =
     "-q: Quiet mode. Don't print output on success.";
 const char kQuiet_Help[] =
     "-q: Quiet mode. Don't print output on success.\n"
     "\n"
     "  This is useful when running as a part of another script.\n";
 
 const char kRoot[] = "root";
 const char kRoot_HelpShort[] =
@@ skipping 129 matching lines @@
   if (info_map.empty()) {
     INSERT_VARIABLE(Args)
     INSERT_VARIABLE(Color)
     INSERT_VARIABLE(Dotfile)
     INSERT_VARIABLE(FailOnUnusedArgs)
     INSERT_VARIABLE(Markdown)
     INSERT_VARIABLE(NoColor)
     INSERT_VARIABLE(Root)
     INSERT_VARIABLE(Quiet)
     INSERT_VARIABLE(RuntimeDepsListFile)
     INSERT_VARIABLE(Threads)

[brettw, 2016/05/13 17:04:15]

Oh, also add here:
  INSERT_VARIABLE(ScriptExecutable)
so it appears in the overview help.

[Petr Hosek, 2016/05/13 18:13:47]

Done.

     INSERT_VARIABLE(Time)
     INSERT_VARIABLE(Tracelog)
     INSERT_VARIABLE(Verbose)
     INSERT_VARIABLE(Version)
   }
   return info_map;
 }
 
 #undef INSERT_VARIABLE
 
 }  // namespace switches