Remove LINK entries in make_global_settings.

LINK isn't looked at by the ninja generator, and since gyp
https://code.google.com/p/gyp/source/detail?r=1721 both make and ninja
default the linker to what's set via CC, which is usually what is desired
anyways.

Since no bots use make anymore, this shouldn't have an observable effect.
Even if the bots were still using make, the default of CC should be make
this an almost-noop.

BUG=none
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/24489002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225200 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225200