"Invalid Library Found" with Adafruit SAMD 1.5.10

[TheShadowhawke]

I am using Arduino 1.8.11, and running into the following warning showing up in the compile window:

Invalid library found in C:\Users<USER>\AppData\Local\Arduino15\packages\adafruit\hardware\samd\1.5.10\libraries\CI_Tests: no headers files (.h) found in C:\Users<USER>\AppData\Local\Arduino15\packages\adafruit\hardware\samd\1.5.10\libraries\CI_Tests

This warning has started since installing the Adafruit SAMD boards version 1.5.10. It does not appear to affect compiling, but it does get spammed as the issue is detected.

[ladyada]

@hathach want to add a fake header to make it happy?