F/mongodb makefile cleanup

[bazsi]

This series encodes hard-wired paths into a single variable and also removes the generation of dummy.c, which was a phony target.

I am not exactly sure what the original intention was behind those, but I think it is better this way.

@algernon, you seem to have created this solution in the first place. The original commit 27ac7d4 states that make dist failed otherwise.

I just did a make dist with --disable-mongodb, which really turned off ENABLE_MONGODB but still the tarball produced by make dist did include mongo-c-driver

I am producing a similar patch to afamqp, but first I'd like to have an opinion on this PR.

[bazsi]

one more note, the reason I wanted to remove dummy.c is that it always caused the mongodb/amqp module to be rebuilt, even if I invoked "make check" and that was slowing down my TDD cycles.

[algernon]

Oh boy. It was some "weird" autotools behaviour I wanted to work around. If you did --disable-mongodb --without-libmongo-client, that's when stuff broke. Disabling only one, and leaving the other on default did not trigger the issue.

The main reason for dummy.c was to trigger a build of the submodule, before building the plugin. There may be better ways to do it now.

[bazsi]

This now seems to work for me and does not need the dummy.c file. It still links libafmongodb.la all time I invoke "make check", but I don't see how we could avoid that, but at least it doesn't compile an empty dummy.c file

I consider this branch ready now.

[bkil-syslogng]

👍 I didn't test this, but from the code, it shouldn't make matters worse. The said rebuilding and the dummies were an eye sore for me as well.

[bazsi]

I am merging this based on the last comment and it doesn't really touch code and travis should cover checking this and travis is green.

The only problem this can cause is that amqp and/or mongodb will not be rebuilt in case it would need to be rebuilt. that case only affects developers not end users and I hope that target group can figure this out if she/he is hacking on the codebase.