make: try to invalidate the cache, but only if the system looks like it
make: try to invalidate the cache, but only if the system looks like it

`install' has the same issue as `upgrade' and maybe we need to be careful
about use of `-[pP]' so that we are not stuck with a hash that does not
invalidate when installing a new version anymore.

opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core,opnsense/core