forge communications install failure on Mac: missing octave/config.h

[Andrew Janke]

Hi, Octave maintainers,

I'm having trouble installing the Forge communications package on macOS.
Affects 4.4.1 and 5.1.0. Happens in both Octave.app and a vanilla Octave.

Looks like the problem is that communications wants to use the
octave/config.h header file, but it's not present in the Octave
installation.

>> pkg install -forge communications
[...]
In file included from galoisfield.cc:21:
./galois.h:24:10: fatal error: 'octave/config.h' file In file included
from notgalois-def.cc :found21:

./galois.h:24:10: fatal error: 'octave/config.h' file not found
#include <octave/config.h>
         ^~~~~~~~~~~~~~~~~
#include <octave/config.h>
         ^~~~~~~~~~~~~~~~~
galois.cc:21:10: fatal error: 'octave/config.h' file not found
#include <octave/config.h>
         ^~~~~~~~~~~~~~~~~
1 error generated.
1 error generated.
make: *** [galois-def.o] Error 1
make: *** Waiting for unfinished jobs....
make: *** [galoisfield.o] Error 1
1 error generated.
make: *** [galois.o] Error 1
cyclgen.cc:32:17: warning: 'length' is deprecated
[-Wdeprecated-declarations]
  int x_len = x.length ();


[/Applications/Octave-4.4.1.app/Contents/Resources/usr/Cellar/octave-octave-app@4.4.1/4.4.1]
$ find . -name config.h
[/Applications/Octave-4.4.1.app/Contents/Resources/usr/Cellar/octave-octave-app@4.4.1/4.4.1]
$


Does something special need to be done to get the Octave build process
to install octave/config.h? Or is this maybe a bug in the build system?
Or should packages not be using octave/config.h?

Original user report: https://github.com/octave-app/octave-app/issues/35

Cheers,
Andrew