On AIX, I see the following:

  CCLD     src/cppi
ld: 0711-317 ERROR: Undefined symbol: .pthread_mutex_lock
ld: 0711-317 ERROR: Undefined symbol: .pthread_mutex_unlock
ld: 0711-345 Use the -bloadmap or -bnoquiet option to obtain more information.
collect2: error: ld returned 8 exit status

This is due to some gnulib functions using mbrtoc32, etc. which use
locks.

The following patch adds the link flags.

Collin