McStas 3.1 macOS/Intel was built on macOS 12

[willend]

(May prevent execution of the code-generator on macOS 10)

Test should be carried out wrt. the other "current" McStas and McXtrace releases, plus we should decide on which releases are in fact supported.

[willend]

McStas: 2.7.1 similarly reports built for macOS 11. (Outdated 3.0 also does not run on earlier releases than 10.15 it seems...)

McXtrace: 3.0 similar issue related: https://github.com/McStasMcXtrace/McCode/issues/1229