build.sh:-R: always print/don't print std{out,err} logs for failed packages.
    build.sh:-vv: always print/don't print stdout logs for successfully built packages.
    subr/ex_rtl_fileop.subr:ex_build_fileop(): log at vvvo (-vvv.)
    subr/ex_rtl_log.subr, vars/env.vars: removes [vw]arn, separates info & {vnfo,vvfo,vvvo}.
    var/env.vars:${CLEAR_ENV_VARS_EXCEPT}: adds ARG_VERBOSE[23].