SPI SS (PB0) pin is inaccessible on Pro Micro #76
Description
It is essential to have access to the SS pin in SPI slave mode, but on Pro Micro board the pin is connected to RX LED.
While it is possible to desolder the resistor attached to the pin, board's software still controls it: switches it to OUTPUT mode when USB is connected and changes its level when data is received.
It would be great have an ability to disable this behavior, for example, with -D SOME_MACRO compiler option.