problem with subdir-objects and not found .Plo files when migrating to 1.14

[Sergey 'Jin' Bostandzhyan]

Hi,

I have a project that compiles perfectly under automake 1.11 and 1.12,
but the scripts give warnings with 1.14, complaining that source file
xyz is in a subdirectory, but option 'subdir-objects' is disabled.

So, I simply enabled the above option, thinking that this would do the trick,
however then I can't compile anymore, because .Plo files are not found, i.e.:
toxcore/.deps/libtoxcore_la-DHT.Plo: No such file or directory

Disabling automatic dependency tracking by adding the no-dependencies
solves the problem, but I do not consider this a nice solution.

>From what I understand the subdir-objects feature will be required in 2.0,
so as much as I would like to ignore it - I guess I'll have to find a clean
fix for this issue, preferably one that would work with automake 1.11 and
1.14 (and later).

My setup:

I have two Makefile.am files, one on top level which is not doing much,
except for EXTRA_DIST'ing a couple of things, it has one level of recursion,
i.e SUBDIRS = build

The build/Makefile.am includes a bunch of logically organized .inc files that
list individual sources.

The idea is that all object and all executable files go to the build directory.

Yes, I do know that it is possible to build "out of the tree" to keep
compiled files separate from the sources, however, especially during
development, it is often more convenient to simply be able to type "make" at
the top level, instead of having to navigate to some out of tree directory.

If you'd like to have a look:
https://github.com/jin-eld/ProjectTox-Core/tree/automake-portability

Is it possible to keep the logic with the in-tree build directory with
automake 1.14? I did try to move all the logic from build/Makefile.am into
the top level Makefile.am and removing build/Makefile.am completely, but
it does not help - .Plo files are not found.

So right now I can either remove subdir-objects and I will get the warnings,
or I can add it, but then the build fails.

How do I solve this cleanly? Am I doing anything "illegal" or is it a
limitaion or even a bug in 1.14?

Kind regards,
Jin