cmGeneratorTarget: Clear AllConfigSources in ClearSourcesCache
In !701 (merged) we forgot to update ClearSourcesCache
to also clear AllConfigSources
. This leads to subtle cases where code paths like PCH handling that add sources during generation break depending on ordering.
Suggested-by: Christian Fersch
Fixes: #20712 (closed), #20702 (closed)
Backport: release