The test main.myisampack is failing with message:
myisamchk: error: myisam_sort_buffer_size is too small
It works fine on all other arches I tested: s390 (32 and 64), i686, x86_64 or ppc64.
Even though I don't have direct access to any ppc32 I was able to put some outputs into the code and run it on a building machine. It really seems like buffer limit (sortbuff_size variable) is 0 when entering function _create_index_by_sort() at mariadb-5.5.29/storage/myisam/sort.c:104
I suspect some bad work with memory, especially with variable sizes. Particularly sort_buffer_size defined at mariadb-5.5.29/storage/myisam/ha_myisam.cc:77 seems to be ULONGLONG but the minimum value is casted to (long).
Similar situation is in mariadb-5.5.29/storage/myisam/myisamchk.c:295 where myisam_sort_buffer_size uses casting to long but after then we use it as ulonglong.
This is probably all the info I can provide right now, but I'll be happy to test a potential patch.