bug#68151: automake-1.16j on Alpine Linux

[Karl Berry]

  - does not understand the option '--best', only '-1' ... '-9'.
  - understands the options '-1' ... '-9' only when compressing, not when

Seems a rather unnecessary incompatibility that some system decided not
to support --best in gzip, when it has been available for those same 30
years. Oh well.

    Here's a proposed fix. It consists in passing '-9' instead of '--best'.

Thanks. Looks fine to me, and all the tests still passed. Installed,
with a few words in the doc. -k