[autogen] Honor environment variables and prefer autoreconf.
[autogen] Honor environment variables and prefer autoreconf.

tstack/lnav,acleasby/lnav,tstack/lnav,acleasby/lnav,sureshsundriyal/lnav,sureshsundriyal/lnav,acleasby/lnav,sureshsundriyal/lnav,tstack/lnav,acleasby/lnav,acleasby/lnav,tstack/lnav,sureshsundriyal/lnav