clang/make: Set LINK to $(CXX).

Fixes clients that set CXX to a custom clang, such as ASAN.

BUG=none
TEST=asan bot goes green again.

Review URL: http://codereview.chromium.org/7838013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@99868 0039d316-1c4b-4281-b951-d872f2087c98

build/common.gypi

@@ -2016,7 +2016,7 @@
       'make_global_settings': [
         ['CC', 'third_party/llvm-build/Release+Asserts/bin/clang'],
         ['CXX', 'third_party/llvm-build/Release+Asserts/bin/clang++'],
-        ['LINK', 'third_party/llvm-build/Release+Asserts/bin/clang++'],
+        ['LINK', '$(CXX)'],
         ['CC.host', '$(CC)'],
         ['CXX.host', '$(CXX)'],
         ['LINK.host', '$(LINK)'],