[GN] Use "xcrun" instead of "xcodebuild" to get information on SDK.

build/config/mac/sdk_info.py

Index: build/config/mac/sdk_info.py
diff --git a/build/config/mac/sdk_info.py b/build/config/mac/sdk_info.py
index ad4ad9e98975d8b7d38c60696ed9d7fa5305b196..c343aa1bd1dd93a0962d489d3213b758f71fed9d 100644
--- a/build/config/mac/sdk_info.py
+++ b/build/config/mac/sdk_info.py
@@ -35,11 +35,12 @@ def FillMachineOSBuild(settings):
 
 def FillSDKPathAndVersion(settings, platform):
   """Fills the SDK path and version for |platform| into |settings|."""
-  lines = subprocess.check_output(['xcodebuild', '-version', '-sdk',
-      platform, 'Path', 'SDKVersion', 'ProductBuildVersion']).splitlines()
-  settings['sdk_path'] = lines[0]
-  settings['sdk_version'] = lines[1]
-  settings['sdk_build'] = lines[2]
+  settings['sdk_path'] = subprocess.check_output([
+      'xcrun', '-sdk', platform, '--show-sdk-path']).strip()
+  settings['sdk_version'] = subprocess.check_output([
+      'xcrun', '-sdk', platform, '--show-sdk-version']).strip()
+  settings['sdk_build'] = subprocess.check_output([
+      'xcrun', '-sdk', platform, '--show-sdk-build-version']).strip()

[Nico, 2016/05/18 11:21:06]

Hm, my xcrun doesn't know --show-sdk-build-version yet. I'm on Xcode 7.0. Some
of the bots are on 5.0 still I think.

Since this computes xcode_version above, maybe this could check if the
xcode_version is new enough and if so call xcrun and else call xcodebuild to get
it?

Why is this field needed at all? gyp never queries for ProductBuildVersion as
far as I can tell.

It does query --show-sdk-build-version, but only:

      if xcode >= '0720':
        cache['DTSDKBuild'] = self._GetSdkVersionInfoItem(
            sdk_root, '--show-sdk-build-version')
      elif xcode >= '0430':
        cache['DTSDKBuild'] = sdk_version
      else:
        cache['DTSDKBuild'] = cache['BuildMachineOSBuild']

(where sdk_version is the result from --show-sdk-version)

Can we do the same here (we can assume 4.3), with a TODO to unconditionally use
--show-sdk-build-version once all bots are on Xcode 7.2?

[sdefresne, 2016/05/18 14:45:02]

I don't know why gyp does not use it, but when I build downstream, the value
that ends up in my Info.plist is the value returned by "xcrun -sdk iphoneos
--show-sdk-build-version". I also get the same value when I build with
xcodebuild so it is possible that it comes from one environment variable set by
Xcode when it invokes ninja in hybrid build mode.

I can remove it but then I have a diff when I compare the output of
gyp/xcodebuild and gn builds.

 
 
 if __name__ == '__main__':