Fix distdir target in case of system option

[Kokan]

The following dependencies (as git submodules) were optional to include into the dist compressed files:

• ivykis
• librabbitmq-c
• mongoc

This should be only in case of internal option, and not in case of system, as the system shall provide those files.

Signed-off-by: kokan peter.kokai@balabit.com

[kira-syslogng]

Build SUCCESS, the tests were executed on test branch: master and test suite: functions

[MrAnno]

Please note that we've fixed issues such as #1204 and #1442 previously, to include all submodules in the dist tarball (no matter how syslog-ng was configured before the make dist command).

This PR violates this idea.
We discussed the problem IRL, and I don't mind if we break it. I just wanted to leave a note here to remember to discuss this before merging the PR.

[MrAnno]

We agreed that this can be merged.

TODO: check all submodules in configure (all should be "internal" by default)

[MrAnno]

defaults:

• mongoc: auto (system by default if exists)

• jsonc: auto (internal? by default if exists)

• rabbitmq: internal

• ivykis: internal

[kira-syslogng]

Build SUCCESS, the tests were executed on test branch: master and test suite: functions

[Kokan]

The make dist in the current format creates a compressed file containing a few extra files with dependencies (also attached as git submodules). Therefore a compressed file exists, where all of the ./configure option shall work. But those extra dependencies are just external project. It is nice to keep tracking the working version in such way, and to ensure the proper function. Also a great place for confusion, the user could want more control such as not included next to syslog-ng addition files such as jsonc or rabbitmq-c. The autogen.sh option for skip_submodules also points to this direction, which is already part of the syslog-ng. Of course the default is to include those files.

[lbudai]

@Kokan : so the default distribution tarball contains everything, as before, but we have the chance for customizing the dist. tarball (what we currently need in some of our internal build environments).

[lbudai]

it could be interest to you (as I know, you are build your own dist tarballs) :
@czanik
@mochrul

[czanik]

@lbudai : Thanks! Tested and I had no problem building syslog-ng from my own dist tarball on openSUSE / SLES / EPEL7