JDK9: RFR: 8033898: undefined symbol when build hotspot with Xcode5

[Henry Jen]

Hi,

Please review a simple webrev that ensure we link with libstdc++ when 
using clang instead of libc++, libc++ is default for Xcode5.

Per clang man page,

       -stdlib=library
           Specify the C++ standard library to use; supported options are
           libstdc++ and libc++.

Bug: https://bugs.openjdk.java.net/browse/JDK-8033898
Webrev: http://cr.openjdk.java.net/~henryjen/jdk9/8033898/1/webrev/

Cheers,
Henry