[UBsan] Enable ubsan minimal unit tests on OpenBSD

OpenBSD needs lld linker for sanitisers.
Disabling lint checking as some symbols cannot be defined and block the proper unit tests launch.

Reviewers: lebedev.ri, vitalybuka

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D48528

llvm-svn: 335524