ci: automatically clear config.cache if it cannot be used

ci: automatically clear config.cache if it cannot be used

Summary:
if env vars change between runs then the cache is invalidated, causing
configure to print a very specific error

by running a separate script to catch this error, the build can detect
and clear the cache when necessary to avoid having to manually disable
the cache when changing build settings
Depends on D6697

Reviewers: stefan_schmidt, bu5hm4n

Reviewed By: bu5hm4n

Subscribers: bu5hm4n, cedric, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D6732