Add NetBSD support in lsan_interceptors.cc

Summary:
NetBSD is a modern POSIX-like UNIX-like Operating System derived from 4.4BSD/386BSD.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, vitalybuka, kcc, dvyukov

Reviewed By: kcc

Subscribers: llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D37307

llvm-svn: 312184