I cloned mruby-esp32, and tried the examples.
While simplest and system worked, wifi_example did not work.

When just editing the ssid and password, it crashes with a stack overflow
https://gist.github.com/ndac-todoroki/a01a35f956bb5159b49b9f3d6bce2cd4

and commenting out the loop do ... end results in a error somewhere around the garbage collection.
https://gist.github.com/ndac-todoroki/1465c52f97f195b864767849dbdcacc9

I'm compiling and uploading the file from Ubuntu 17.04 with gcc 7.2.0 .
and the latest idf tools.
Does this still work on your mac OS?