_sysconfigdata.py includes information about how to build extension modules. On AIX this requires a wrapper script to build shared libraries.  The file includes definitions like:

 'BLDSHARED': './Modules/ld_so_aix gcc -pthread -bI:./Modules/python.exp',
 'LDSHARED': './Modules/ld_so_aix gcc -pthread -bI:./Modules/python.exp',
 'LINKCC': './Modules/makexp_aix Modules/python.exp . libpython3.4dm.a;  gcc '
           '-pthread',
 'MAKESETUP': './Modules/makesetup',

which is correct in the build directory, but is not correct for the install directory.  The paths do not correspond to the installed location of ld_so_aix and makexp_aix in lib/pythonX.Y/config .