update config.guess for rtcmix
The config.guess in
externals/rtcmix-in-pd/RTcmix-pd-4.0.1.6
is too old. It can't properly identify the msys2 system Purr Data is using to build on Windows.
The config.guess in
externals/rtcmix-in-pd/RTcmix-pd-4.0.1.6
is too old. It can't properly identify the msys2 system Purr Data is using to build on Windows.