[cppyy] Use cppdef for variable in test

[hahnjo]

This fixes test22_cppexec which was marked as xfail if not IS_WINDOWS, which is the opposite of the given reason "Fails on Windows".

[guitargeek]

LGTM, thanks!

By the way, I think cppexec should work in principle, because it's the wrapper around gInterpreter->ProcessLine. And statements like gInterpreter->ProcessLine("int interactive_b = 4") do work in C++, so I don't see why they should not work in Python. You have any thoughts on this? I would like to understand what's going on there, to understand the interpreter better 🙂 Not a problem for this PR though, because it doesn't matter if we use cppexec or cppdef to implement the test for the interactive access to the Cling global scope.

[vepadulano]

FWIW, I also don't understand why cppdef would be more correct than cppexec in this case

[github-actions]

Test Results

    21 files      21 suites   3d 4h 53m 31s ⏱️
 3 854 tests  3 853 ✅ 0 💤 1 ❌
73 303 runs  73 302 ✅ 0 💤 1 ❌

For more details on these failures, see this check.

Results for commit 2241db2.

♻️ This comment has been updated with latest results.

[hahnjo]

My understanding is that cppexec is to evaluate an expression. That's why I think cppdef is more appropriate here, and it seems to solve the issue with the test.