[PATCH] NEWS: Mention testing glibc build with different compilers

[Paul Zimmermann]

       HJ,

> How about this?
> 
> * Support testing glibc build with a different C compiler or a different
>   C++ compiler from the C and C++ compilers used to build glibc with
> 
>   $ ../configure TEST_CC="gcc-6.4.1" TEST_CXX="g++-6.4.1"
> 
>   And support testing glibc build with Clang
> 
>   $ ../configure TEST_CC="clang" TEST_CXX="clang++"
> 
>   Some run-time failures with Clang are expected.

this is fine for me.

Thank you!

Paul