bug#24862: guile 2.0.13 build error under macOS 10.12 Sierra

[Matt Wette]

(lldb) n
Process 85754 stopped
* thread #1: tid = 0xe66f2, 0x000000010002c03f 
guile`scm_i_mkstemp(tmpl=0x0000000104cd09a0, mode=0x0000000100ea34c0) + 238 at 
filesys.c:1490, queue = 'com.apple.main-thread', stop reason = step over
    frame #0: 0x000000010002c03f guile`scm_i_mkstemp(tmpl=0x0000000104cd09a0, 
mode=0x0000000100ea34c0) + 238 at filesys.c:1490
   1487     }
   1488 
   1489   SCM_SYSCALL (rv = mkostemp (c_tmpl, open_flags));
-> 1490   if (rv == -1)
   1491     SCM_SYSERROR;
   1492 
   1493   scm_substring_move_x (scm_from_locale_string (c_tmpl),
(lldb) p rv
(int) $8 = -1
(lldb)