[SanitizeCoverage] Enable stack-depth coverage for -fsanitize=fuzzer
Summary:
- Don't sanitize __sancov_lowest_stack.
- Don't instrument leaf functions.
- Add CoverageStackDepth to Fuzzer and FuzzerNoLink.
- Disable stack depth tracking on Mac.
Reviewers: vitalybuka, kcc, george.karpenkov
Reviewed By: kcc
Subscribers: kubamracek, cfe-commits, llvm-commits, hiraditya
Differential Revision: https://reviews.llvm.org/D37156
llvm-svn: 312026