Rename tsan_interceptors.cpp into tsan_interceptors_posix.cpp

Summary:
It's needed to use __GLIBC_PREREQ from <features.h>

tsan didn't let us to include <features.h> by using --sysroot=. to disable system includes on
anything that is not named as "tsan*posix*", "tsan*mac*", "tsan*linux*".
See compiler-rt/lib/tsan/CMakeLists.txt

Reviewers: eugenis, dvyukov, kcc

Reviewed By: kcc

Subscribers: mgorny, #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D68176

llvm-svn: 373282