gawk: remove readline support

[ryandesign (Ryan Carsten Schmidt)]

Every time readline is updated to a new major version and its library version changes, gawk must be revbumped to rebuild with that new library. Similarly, whenever ncurses is updated to a new major library version, readline must be revbumped.

Autotools-based software automatically uses gawk if it is installed, even if the port doesn't declare a dependency on it. This causes error messages if the user hasn't upgraded gawk first, with no clear indication that that's what they have to do to solve it. See ProblemHotlist#ncurses6 for a similar problem. These users often file bug reports, and we close them as wontfix because we don't want to add a gawk dependency to every autotools port.

But another solution would be to remove readline support from gawk. Readline provides assistance for interactive text editing, and gawk is usually used noninteractively, so this removal should not affect any ports that use gawk, and should affect only those few users who actually use gawk's interactive mode. Users who do want readline support in gawk's interactive mode could still use rlwrap gawk.

[Schamschula (Marius Schamschula)]

As I was hit by this issue myself after the recent readline update, I concur. I propose to move readline support to a variant, with a note about issues when readline gets an upgrade.

[Schamschula (Marius Schamschula)]

Of course, adding a note that those who do need readline support should install the rlwrap port would also be an option.

[Schamschula (Marius Schamschula)]

In 377c3ca3ed1cf9c87c5f08b76cd557e1f0c16673/macports-ports (master):

gawk: remove readline support

Closes: #58011