Use the SAMD21 SWCLK pin as output has a bug

Using the SAMD21 SWCLK (pin45) as digital output has a bug, it requires a patch, see here:

const int SWCLK = 32;
  pinMode(SWCLK, INPUT); // patch to use the SWCLK pin as output
  pinMode(SWCLK, OUTPUT);
  digitalWrite(SWCLK, 0);