luajit: add host variant

the goal is to use host-luajit with pkg-luarocks
when luajit is on the selected luainterpreter for the target

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
luainterpreter: add host variant

host-luainterpreter is host-lua or host-luajit

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
luarocks: allow to work with host-luainterpreter

when we embed luajit on target,
we use luarocks with host-luajit instead of host-lua,
in order to use the same interpreter on the both side.

Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>