Stefan Agner authored Jun 17, 2020 and Daniel Stone committed Aug 17, 2020

Allow to disable GBM modifiers at runtime using the environment variable
WESTON_DISABLE_GBM_MODIFIERS.

This can be useful for debugging or when modifiers cause issues, e.g. in
case modifiers use higher memory bandwidth and hence impose a lower
resolution limit as it is the case with Intel Kaby Lake graphics.

Related to: #404


Signed-off-by: Stefan Agner <stefan@agner.ch>