[asan] change the coverage collection scheme so that we can easily emit coverage for the entire process as a single bit set, and if coverage_bitset=1 actually emit that bitset

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224789 91177308-0d34-0410-b5e6-96231b3b80d8
4 files changed