comms/libusbsio: fix installation where ARCH != MACHINE_CPU

install -m 0644 /wrkdirs/usr/ports/comms/libusbsio/work/libusbsio-8577280966ee91cab606df5b0c64889be71ce7b9/bin/freebsd_powerpc64le/libusbsio.a /wrkdirs/usr/ports/comms/libusbsio/work/stage/usr/local/lib
install: /wrkdirs/usr/ports/comms/libusbsio/work/libusbsio-8577280966ee91cab606df5b0c64889be71ce7b9/bin/freebsd_powerpc64le/libusbsio.a: No such file or directory