Fix buildgo.sh script to fix linux build failure due to changes in ad1466f8.

The above change used a binary literal that is not supported in c++11 mode when
using gcc. It was formalized into the c++14 standard and works when using that
mode to compile, so change the script to use c++14 instead.

Reviewed by: dvyukov

Differential Revision: https://reviews.llvm.org/D77111