How does --with-wine64 work?

[Austin English]

Vincent asked me to get add a --with-wine64 option to my build script.
I was testing around, and can't seem to get it to work:
$ mkdir - p $HOME/wine{32,64}
$ cd $HOME/wine64
$ ~/wine-git/configure --enable-win64
$ make -j4
$ cd $HOME/wine32
$ ~/wine-git/configure --with-wine64=~/wine64
...
> checking for the directory containing the Wine tools... configure: error: could not find Wine tools in ~/wine64/

~/wine-git/configure --with-wine64=~/wine64/tools/
...
checking for the directory containing the Wine tools... configure:
error: could not find Wine tools in ~/wine64/tools/

What am I missing? Perhaps it needs to be installed somewhere first?