Add more autotools/gmake NetBSD glue

Summary: This diff approaches building the project natively on NetBSD with the autoconf/gmake framework.

Patch by Kamil Rytarowski. Thanks!

Reviewers: emaste, clayborg

Subscribers: tberghammer, joerg, brucem, lldb-commits

Differential Revision: http://reviews.llvm.org/D14531

llvm-svn: 253153