Set SDKROOT in the project-wide xcode_settings block instead of doing it in target_defaults.  This is equivalent to how Xcode sets SDKROOT from the Project Info window's General tab.  Making this setting project-wide means that the selected SDK will show up properly in that UI.
Set SDKROOT in the project-wide xcode_settings block instead of doing it in
target_defaults.  This is equivalent to how Xcode sets SDKROOT from the
Project Info window's General tab.  Making this setting project-wide means
that the selected SDK will show up properly in that UI.

BUG=26976
TEST=Build still works.
     SDK (typically "Mac OS X 10.5") shows up in Project Info:General.
Review URL: http://codereview.chromium.org/371035

git-svn-id: http://src.chromium.org/svn/trunk/src@31307 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: a9b50da0eeafe51595de5150c141007384f2ef87
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser