Get the proper Mac SDK path for the GN build.

This gets the path from xcodebuild rather than hardcoding it in the .gn files.

R=thakis
BUG=

Review URL: https://codereview.chromium.org/136793020

git-svn-id: http://src.chromium.org/svn/trunk/src/build@245403 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

config/mac/mac_sdk.gni

@@ -12,16 +12,23 @@ declare_args() {
   mac_sdk_path = ""
 }
 
+find_sdk_args = [ "--print_sdk_path" ]
 if (is_chrome_branded && is_official_build) {
-  find_sdk_args = [ "--verify", mac_sdk_min "--sdk_path=" + mac_sdk_path ]
+  find_sdk_args += [ "--verify", mac_sdk_min "--sdk_path=" + mac_sdk_path ]
 } else {
-  find_sdk_args = [ mac_sdk_min ]
+  find_sdk_args += [ mac_sdk_min ]
 }
-# Use "list lines" and take the first to get version string without a newline.
+# The tool will print the SDK path on the first line, and the version on the
+# second line.
 find_sdk_lines =
     exec_script("//build/mac/find_sdk.py", find_sdk_args, "list lines")
-mac_sdk_version = find_sdk_lines[0]
+mac_sdk_version = find_sdk_lines[1]
 if (mac_sdk_path == "") {
-  mac_sdk_root = "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX"
-  mac_sdk_path = mac_sdk_root + mac_sdk_version + ".sdk"
+  # TODO(brettw) http://crbug.com/335325  when everybody moves to XCode 5 we
+  # can remove the --print_sdk_path argument to find_sdk and instead just use
+  # the following two lines to get the path. Although it looks longer here, it
+  # saves forking a process in find_sdk.py so will be faster.
+  #mac_sdk_root = "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX"
+  #mac_sdk_path = mac_sdk_root + mac_sdk_version + ".sdk"
+  mac_sdk_path = find_sdk_lines[0]
 }

mac/find_sdk.py

@@ -31,6 +31,9 @@ def main():
   parser.add_option("--sdk_path",
                     action="store", type="string", dest="sdk_path", default="",
                     help="user-specified SDK path; bypasses verification")
+  parser.add_option("--print_sdk_path",
+                    action="store_true", dest="print_sdk_path", default=False,
+                    help="Additionaly print the path the SDK (appears first).")
   (options, args) = parser.parse_args()
   min_sdk_version = args[0]
 
@@ -73,6 +76,10 @@ def main():
     print >>sys.stderr, ''
     return min_sdk_version
 
+  if options.print_sdk_path:
+    print subprocess.check_output(['xcodebuild', '-version', '-sdk',
+                                   'macosx' + best_sdk, 'Path']).strip()
+
   return best_sdk