emulation on host: allow parallel compilation units (#8574)
emulation on host: allow parallel compilation units (#8574)

-j option wasn't passed to recursive 'make' calls
esp8266/Arduino,esp8266/Arduino,sticilface/Arduino,esp8266/Arduino,sticilface/Arduino,esp8266/Arduino,esp8266/Arduino,sticilface/Arduino,sticilface/Arduino,sticilface/Arduino