Thread safety for FastCaloSim
Following !39035 (merged), FastCaloSim ran single-threaded in AthenaMT giving results consistent with Athena
However, there were persistent differences between single-threaded and multi-threaded results from FCS.
I eventually tracked this down to the use of CLHEP::RandGauss, which @jchapman confirmed should be replaced by CLHEP::RandGaussZiggurat
This is sufficient for full MT vs ST agreement, in my tests at least.
Tagging @ahasib