[asan] Complete the Fuchsia port

Submitted on behalf of Roland McGrath.

Reviewers: kcc, eugenis, alekseyshl, vitalybuka

Reviewed By: vitalybuka

Subscribers: filcab, vitalybuka, srhines, kubamracek, mgorny, phosek, llvm-commits

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D35865

llvm-svn: 310431