Fix XCode emulation when SDK is not installed.

pylib/gyp/xcode_emulation.py

Index: pylib/gyp/xcode_emulation.py
diff --git a/pylib/gyp/xcode_emulation.py b/pylib/gyp/xcode_emulation.py
index 47f9d520e10e0206be9cc7d32df2eedc61db57ea..c002b112c54ceef58bd4c5053930aa59bafd37d7 100644
--- a/pylib/gyp/xcode_emulation.py
+++ b/pylib/gyp/xcode_emulation.py
@@ -1479,6 +1479,8 @@ def _GetXcodeEnv(xcode_settings, built_products_dir, srcroot, configuration,
     sdk_root = xcode_settings._SdkRoot(configuration)
     if not sdk_root:
       sdk_root = xcode_settings._XcodeSdkPath('')
+    if sdk_root is None:
+      sdk_root = ''
     env['SDKROOT'] = sdk_root

[Nico, 2015/06/29 16:25:19]

Is it useful to set SDKROOT to an empty string? Should this just be

  if sdk_root is not None:
    env['SDKROOT'] = sdk_root

[sdefresne, 2015/06/29 16:48:59]

IIUC this CL is to get Xcode emulation working when SDK is not installed. I'm
not sure if it is possible to install Xcode without installing a SDK, and since
this variable is only used by Xcode and its command line tools, I don't think
exporting or not the environment variable has any impact.

I'd tend to favor the code that does not export the variable then.

 
   if not additional_settings: