build: linking CoreFoundation framework for OSX

Linking CoreFoundation for OSX is needed for OSX debugging features to
function properly.

For instance Instruments cannot record Heap Allocations if the
CoreFoundation is not linked.

Reviewed-By: Fedor Indutny <fedor@indutny.com>

node.gyp

@@ -319,6 +319,9 @@
           'defines': [ '__POSIX__' ],
         }],
         [ 'OS=="mac"', {
+          # linking Corefoundation is needed since certain OSX debugging tools
+          # like Instruments require it for some features
+          'libraries': [ '-framework CoreFoundation' ],
           'defines!': [
             'PLATFORM="mac"',
           ],