GN: Get Mac build working for IPC target at least.

build/config/sysroot.gni

Index: build/config/sysroot.gni
diff --git a/build/config/linux/sysroot.gni b/build/config/sysroot.gni
similarity index 74%
rename from build/config/linux/sysroot.gni
rename to build/config/sysroot.gni
index 4d14915ecdebb6d8c3c7856199b9ea28647cffe0..b6a213a71f8c463e0dc5dff302ea730d8066de09 100644
--- a/build/config/linux/sysroot.gni
+++ b/build/config/sysroot.gni
@@ -20,8 +20,14 @@ if (is_linux && is_chrome_branded && is_official_build && !is_chromeos) {
   }
 } else if (is_mac) {
   # Set which SDK to use.
-  # TODO(brettw) this needs to be configurable somehow.
-  sysroot = "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk"
+  if (is_chrome_branded && is_official_build) {
+    find_sdk_args = ["--verify", mac_sdk_min "--sdk_path=" + mac_sdk_path]

[bbudge, 2014/01/07 22:31:23]

I'm probably missing some escaping on the last argument. Not sure if this will
work anyway.

+  } else {
+    find_sdk_args = [mac_sdk_min]
+  }
+  mac_sdk_version =
+      exec_script("//build/mac/find_sdk.py", find_sdk_args, "list lines")
+  sysroot = "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX" + mac_sdk_version[0] + ".sdk"
 } else {
   sysroot = ""
 }