deps: improve performance of external dependency checks
deps: improve performance of external dependency checks

This is especially important now that the Lua library paths
are detected using the dependency check machinery.

keplerproject/luarocks,luarocks/luarocks,keplerproject/luarocks,tarantool/luarocks,tarantool/luarocks,keplerproject/luarocks,luarocks/luarocks,keplerproject/luarocks,luarocks/luarocks,tarantool/luarocks