Do not use pthread_setname_np() if we don't have GLIBC or Android.

Summary:
pthread_setname_np() is a nonstandard GNU extension and isn't available
in every C library. Check before it's usage that GLIBC is available or
that we are targeting Android.

Reviewers: clayborg, ovyalov

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D13019

llvm-svn: 248280