Hello,
Building 64-bit Ruby 2.5.9 on AIX using xlc compiler.

Miniruby hangs during "generating encdb.h".

Call-stacks of the miniruby process:

---------- tid# 24838655 (pthread ID:      1) ----------
0x00000001001267f0  ruby_atomic_compare_and_swap(0x1100636b8, 0x1b15a7001b15a7, 0x1af5a7001af5a7) + 0x30
0x000000010001c058  atomic_sub_nounderflow(0x1100636b8, 0x2000) + 0x58
0x0000000100025880  objspace_malloc_increase(0x1100636b0, 0x1102f8f30, 0x0, 0x2000, 0x200000002) + 0x80
0x000000010001eb8c  objspace_xfree(0x1100636b0, 0x1102f8f30, 0x2000) + 0x4c
0x000000010001ec10  ruby_sized_xfree(0x1102f8f30, 0x2000) + 0x30
0x00000001001e71a4  free_io_buffer(0x1102f8e90) + 0x24
0x00000001001e7394  fptr_finalize(0x1102f8e50, 0x0) + 0x34
0x00000001001e7438  rb_io_fptr_cleanup(0x1102f8e50, 0x0) + 0x58
0x00000001001e7560  io_close_fptr(0x1101ad7c0) + 0xe0
0x00000001001e7674  rb_io_close(0x1101ad7c0) + 0x14
0x0000000100007378  restore_load_file(0xfffffffffffe900) + 0x38
0x00000001000083dc  rb_ensure(0x110023278, 0xfffffffffffe900, 0x110023290, 0xfffffffffffe900) + 0x1bc
0x00000001000009a0  load_file(0x1101ae468, 0x1101ae698, 0x1101ad7c0, 0x100000001, 0xfffffffffffefb0) + 0x60
0x0000000100005688  process_options(0x60000000b, 0xffffffffffff4c8, 0xfffffffffffefb0) + 0xa48
0x0000000100005c50  ruby_process_options(0xb0000000b, 0xffffffffffff4a0) + 0xd0
0x000000010000be70  ruby_options(0xb0000000b, 0xffffffffffff4a0) + 0xd0
0x0000000100000560  main(0xb0000000b, 0xffffffffffff4a0) + 0x60
0x0000000100000268  __start() + 0x70
---------- tid# 21168597 (pthread ID:    258) ----------
0x0900000000168334  __fd_poll(??, ??, ??) + 0xb4
0x000000010011d6c4  poll(0x1102dc6d8, 0x2, 0xffffffffffffffff) + 0x24
0x000000010011d790  timer_thread_sleep(0x110062678) + 0x90
0x000000010011d944  thread_timer(0x110062678) + 0x44
0x09000000005abfe8  _pthread_body(??) + 0xe8

Any suggestions on how to fix this?

Thanks.