Apply Lei Zhang's patch to add easy import of additional environment...

SConstruct

Index: SConstruct
===================================================================
--- SConstruct	(revision 1668)
+++ SConstruct	(working copy)
@@ -508,6 +508,7 @@
   result.Add('mode', 'compilation mode (debug, release)', 'release')
   result.Add('sample', 'build sample (shell, process)', '')
   result.Add('env', 'override environment settings (NAME1:value1,NAME2:value2)', '')
+  result.Add('importenv', 'import environment settings (NAME1,NAME2)', '')

[Kevin Millikin (Chromium), 2009/04/02 12:54:11]

Might be clearer to have the message string:

'import environment settings (NAME1,NAME2,...)'

Also, consider zero-based indexing.  :)

   for (name, option) in SIMPLE_OPTIONS.iteritems():
     help = '%s (%s)' % (name, ", ".join(option['values']))
     result.Add(name, help, option.get('default'))
@@ -626,9 +627,13 @@
     options['arch'] = options['simulator']
 
 
-def ParseEnvOverrides(arg):
+def ParseEnvOverrides(arg, imports):
   # The environment overrides are in the format NAME1:value1,NAME2:value2
+  # The environment imports are in the format NAME1,NAME2

[Kevin Millikin (Chromium), 2009/04/02 12:54:11]

Analogously here.

   overrides = {}
+  for var in imports.split(','):
+    if var in os.environ:
+      overrides[var] = os.environ[var]
   for override in arg.split(','):
     pos = override.find(':')
     if pos == -1:
@@ -726,7 +731,7 @@
   env = Environment(options=opts)
   Help(opts.GenerateHelpText(env))
   VerifyOptions(env)
-  env_overrides = ParseEnvOverrides(env['env'])
+  env_overrides = ParseEnvOverrides(env['env'], env['importenv'])
 
   SourceSignatures(env['sourcesignatures'])