Fixes the build failure after the upgrade to glibc 2.26 in
9bb67d5c1e.
From the cfree(3) manpage:
This function should never be used. Use free(3) instead. Starting with
version 2.26, it has been removed from glibc.
From the glibc 2.26 release notes[1]:
* The obsolete function cfree has been removed. Applications should use
free instead.
[1]: https://sourceware.org/ml/libc-alpha/2017-08/msg00010.html
Signed-off-by: aszlig <aszlig@nix.build>
Cc: @7c6f434c, @tohl
