Allow compiling coverage-enabled v86-debug.wasm and covreport generation
Allow compiling coverage-enabled v86-debug.wasm and covreport generation

Usage:
- make build/v86-debug.wasm ENABLE_COV=1 (assuming the file doesn't already
exist)
- make covreport

copy/v86,copy/v86,copy/v86,copy/v86,copy/v86,copy/v86,copy/v86