Update a comment about `make` verbose option, dropping `Q=` explanation.
    
    According to the <https://bugs.ruby-lang.org/issues/18756>, the `Q=` is not
    recommended. The `V=1` is recommended to output for the verbose mode.
    The `make V=1` suppresses some logs that `make` without `V=1` outputs rather
    than just adding verbose logs.
    
    While the `V=1 ECHO0=echo` is more equivalent with `Q=`, the
    `make V=1 ECHO0=echo` doesn't really output meaningful logs additionally.
    So, the `make V=1` is the best option for us to check the compiler flags.