textproc/flex (/usr/local/bin/flex) shadowed by /usr/bin/flex after install

[Steve Franks]

In maintaining devel/urjtag, I've added a dependancy to textproc/flex.
 On some systems, however, I've found that when textproc/flex gets
installed, it lands in /usr/local/bin, as expected, but there's a
/usr/bin/flex which precedes it in the path - is there a canonical way
to resolve this?  I've just been mv'ing my /usr/bin/flex, but clearly,
I can't add a patch to a port to do that to other people's systems...

Steve