[sanitizer] sancov.py: print status to stderr


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224840 91177308-0d34-0410-b5e6-96231b3b80d8
[sanitizer] Tweak sancov.py output.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@224841 91177308-0d34-0410-b5e6-96231b3b80d8