On FreeBSD, if you are trying to build a port but it fails at the configure step with a message similar to this:

checking build system type... Invalid configuration `arm64-portbld-freebsd13.2': machine `arm64-portbld' not recognized
configure: error: /bin/sh ./build-aux/config.sub arm64-portbld-freebsd13.2 failed

Here’s a quick-fix that might work for you:

export CONFIGURE_TARGET=arm64-unknown-freebsd13.2
make install

This is similar to passing --host arm64-unknown-freebsd13.2 to the configure script instead of trying to guess it.