Fix syntax errors in tests

[mcbarton]

If you inspect the ci you'll see quite a few tests which error due to a syntax error. For example

[779](https://github.com/compiler-research/cppjit/actions/runs/33078956981/job/98540584529?pr=45#step:8:1790)
    E     File "/home/runner/work/cppjit/cppjit/test/test_overloads.py", line 218
    E       @mark.skipif(condition=not not IS_MAC_ARM, condition=IS_MAC, reason="Seg Faults")
    E                                                  ^^^^^^^^^^^^^^^^
    E   SyntaxError: keyword argument repeated: condition

By fixing these syntax errors you might get some more passing tests, but at the very least you'll be able to test things you couldn't test before.

[aaronj0]

I have a patch for this (and improving our testing infra in general) in the ci-workflows cppjit.yml. Will open a PR sometime next week as other things in the pipeline are higher priority.