Fix undefined reference to ulp_count and ulp_entry

[angyongen]

Arduino doesn't seem to be copying the .s files from the sketch directory to the temp directory. This causes the following errors:

undefined reference to 'ulp_count'

undefined reference to 'ulp_entry'.

See issue #78

[tilman1]

Works for me as well... I am using ubuntu 20.04, Arduino 1.8.15, and V1.0.6 of the esp32 core.

[Lowku]

I still get the error when trying to compile the ulpcc example using: ubuntu 20.04, Arduino 1.8.13, and V1.0.3 of the esp32 core

[markwilkie]

This would be great to merge in.....