Create specific target for compile commands

Can we get a target specifically for generating compile_commands.json? I always recommend having a dedicated config for it anyway. In particular, it should use clang, not use icecc or ccache, enable flags that maximize enabled code to improve find-references (especially --dbg=on but there are a few others), and --disable-warnings-as-errors (this plays nicer with its usage inside of IDEs/editors).