buildx.sh: use "mkdir -p" to create $PREFIX_DIR, don't retry
buildx.sh: use "mkdir -p" to create $PREFIX_DIR, don't retry

Improve messages about $PREFIX_DIR

cocoon/xrdp,ubuntu-xrdp/xrdp,neutrinolabs/xrdp,moobyfr/xrdp,ubuntu-xrdp/xrdp,itamarjp/xrdp,itamarjp/xrdp,metalefty/xrdp,metalefty/xrdp,moobyfr/xrdp,itamarjp/xrdp,PKRoma/xrdp,jsorg71/xrdp,moobyfr/xrdp,jsorg71/xrdp,proski/xrdp,ubuntu-xrdp/xrdp,cocoon/xrdp,neutrinolabs/xrdp,proski/xrdp,PKRoma/xrdp,metalefty/xrdp,jsorg71/xrdp,neutrinolabs/xrdp,cocoon/xrdp,proski/xrdp,PKRoma/xrdp