[Slackbuilds-users] Finding why build fails

[Rich Shepard]

I'm trying to build pygobject3-python3 but it fails:
In file included from /usr/include/python3.9/abstract.h:843:0,
                  from /usr/include/python3.9/Python.h:151,
                  from ./pyglib.h:23,
                  from gobjectmodule.c:27:
/usr/include/python3.9/cpython/abstract.h:131:1: error: C++ style comments are not allowed in ISO C90
  // Backwards compatibility aliases for API that was provisional in Python 3.8
  ^
/usr/include/python3.9/cpython/abstract.h:131:1: error: (this will be reported only once per input file)
Makefile:743: recipe for target '_gi_la-gobjectmodule.lo' failed
make[3]: *** [_gi_la-gobjectmodule.lo] Error 1
make[3]: Leaving directory '/tmp/SBo/pygobject-3.18.2/gi'
Makefile:1056: recipe for target 'all-recursive' failed
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory '/tmp/SBo/pygobject-3.18.2/gi'
Makefile:674: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/tmp/SBo/pygobject-3.18.2'
Makefile:497: recipe for target 'all' failed
make: *** [all] Error 2

The only prerequisite is py3cairo so I rebuilt and reinstalled
py3cairo-1.10.0-x86_64-3_SBo.

Since this didn't resolve the pygobject-3.18.2 build failure where do I look
for the reason? (I can provide a full build log if that helps.) I've
encountered 'recipe for target all failed' or 'no target for all' before so
learning what causes it would be really helpful.

TIA,

Rich