Fedora defines shell functions for some commands used by FreeBSD build scripts, make them behave incorrectly for our purposes. For instance 'which which' returns:
```
which ()
{
( alias;
eval ${which_declare} ) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot $@
}
```
instead of
```
/usr/bin/which
```
This patch unsets those functions to restore original/expected behavior