[krbdev.mit.edu #8955] nonportable contsruct in shell script

<URL: https://krbdev.mit.edu/rt/Ticket/Display.html?id=8955 >

I assume this showed up in a scan of all the shell scripts in the tree with
some tool, and wasn't something that caused a problem in practice? The ccapi
directory only gets built on Windows (and used to get build as part of Kerberos
for Macintosh, but that's long defunct).