Fix shader cache
Recent commits to write the NIR into the cache only once produced failures detected by Intel CI for dEQP and webgl.
Reverting 2 problematic commits produced clean results:
http://mesa-ci-results.jf.intel.com/majanes/builds/287/group/63a9f0ea7bb98050796b649e85481845
The android build failure shown in that run is due to #2129 (closed)