[sanitizer_common] Fuchsia-specific implementation of SanitizerCoverage

Submitted on behalf of Roland McGrath.

Reviewers: kcc, eugenis, alekseyshl, vitalybuka

Reviewed By: kcc

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

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D35866

llvm-svn: 309797