[hwasan] Add -hwasan-with-ifunc flag.

Summary: Similar to asan's flag, it can be used to disable the use of ifunc to access hwasan shadow address.

Reviewers: vitalybuka, kcc

Subscribers: srhines, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D50544

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339447 91177308-0d34-0410-b5e6-96231b3b80d8