Add libconfig libevent stunnel zlib build shell script

guowenxue

2019-08-05 2c01607fdda70734dd04e0db3cd3ecb8d741b4c7

linux-bsp/tarballs/linux-at91.tar.xz does not exist in tree 3c49eae8821f733d9ff61ca1885990d9e214d71d