LayerIndex/Checker/Usual Issues

Usual issues that lead to yocto-check-layer failing:

a) The layer does change recipes just by being present

• this means that usually a .bbappend has a change which is not conditional or in other ways inactive until enabled by the user
  • Patterns that can be used for this are:
    • _append_someoverride - to activate the layer, an override needs to be added
    • FOO_ENABLE = "1" and ${@bb.utils.contains('FOO_ENABLE', '1', 'case_yes', 'case_no', d)}
      • e.g. require ${@bb.utils.contains('FOO_ENABLE', '1', 'foo_bar.inc', , d)}