This CL enables generating *.sancov data. Blacklist for sancov tool is provided, too. Sancov tool for report generation needs to be build from llvm compiler-rt sources (llvm 3.9.0 or newer). See http://clang.llvm.org/docs/SanitizerCoverage.html . BUG=webrtc:6136 R=phoglund@webrtc.org TBR=kjellander@webrtc.org Review URL: https://codereview.webrtc.org/2144273002 . Cr-Commit-Position: refs/heads/master@{#13506}