Use apache2ctl modules for Gentoo systems.

[joohoi]

Fixes #5344

[bmw]

This seems simple enough but two questions:

1. What's the behavior of apache2ctl on systems with systemd?
2. Could we use apache2ctl modules on Gentoo? I'm not sure how new this functionality is, but at least on an up to date system, this works. The relevant snippet from /etc/init.d/apache2 is:

modules() {
        checkconfig || return 1
        ${APACHE2} ${APACHE2_OPTS} -M 2>&1
}

EDIT: apache2ctl modules is recognized in the up to date versions of both Apache 2.2 and Apache 2.4.

[joohoi]

Nice catch! Now this PR is doing exactly that, using apache2ctl modules, for the modules call.

Unfortunately I think that systemd version is completely unable to use apache2ctl, as it pretty much calls the OpenRC script directly, the whole contents of apache2ctl being:

#!/bin/sh
exec /etc/init.d/apache2 "$@"                          

And this has also been the main issue for Gentoo systems with systemd. I'm trying to figure out the correct things to do for these systems in #5263

[bmw]

Then my only concern with this PR is will trying to use apache2ctl modules make things worse for systemd users?

I tried to test this myself, but after waiting an hour for things to compile, I'm not sure I did it right. OpenRC was still installed and /etc/init.d/apache2 still works. After Googling around, maybe it OpenRC is always installed unless the user does a lot of work on their end to rip it out of Gentoo. See https://forums.gentoo.org/viewtopic-t-994660.html?sid=2d4170a3eda7addd8e2883e402af733d.

Since I struggled to make this work, I'm trusting your judgement here.

[joohoi]

We don't currently have a reasonable support for Gentoo systems running systemd at all. Even though systemd might be officially supported by Gentoo, the Apache package unfortunately isn't. This is discussed in #3411 .

We need to clean up the constants throughout Apache plugin at some point, and this will also include making the user able to provide the Apache control commands on the command line which in turn will help to alleviate this problem.

In addition to the previous, I'm going to need to have a talk with www-servers/apache package maintainer about the future plans about the package in terms of the apache2ctl control script usage in OpenRC and systemd environments.

[bmw]

Thanks for the link to #3411. This LGTM.