As per info make, it turns out that ifndef SOME_VAR is true for SOME_VAR defined to an empty value. This is unusable for caching, so replace it with ifeq ($(origin SOME_VAR),undefined).Signed-off-by: Jan Lindemann <jan@janware.com>
As per info make, it turns out that ifndef SOME_VAR is true for SOME_VAR defined to an empty value. This is unusable for caching, so replace it with ifeq ($(origin SOME_VAR),undefined).