[OpenMP] FreeBSD address check if mapped more native

/proc unless Linux layer compatibility is activated for CentOS is activated is not present
thus relying on a more native for checking the address.

Reviewers: Hahnfeld, kongyl, jdoerfert, jlpeyton, AndreyChurbanov, emaster, dim

Reviewed By: Hahnfeld

Differential Revision: https://reviews.llvm.org/D67326

llvm-svn: 373152