Commit a0486bac41d6ce47f27795a5abbca5cc53ddba00 breaks build on FreeBSD 12

[Jose E. Marchesi]

Hi.

    Hello Jose,
    
    commit a0486bac41d6ce47f27795a5abbca5cc53ddba00
    Author: Jose E. Marchesi <jose.marchesi@oracle.com>
    Date:   Fri May 31 11:10:51 2019 +0200
    
        libctf: fix a number of build problems found on Solaris and NetBSD
    
    breaks the build on FreeBSD 12:

That was actually a commit in behalf of Nick Alcock (only I forgot to
change the --author.)

Nick, can you please take a look?