[tests] remove hard coded python version from lit tests

[erick-xanadu]

Context: Recently upgraded OS in my virtual machine. Reinstalled from scratch. Noticed this hard coded version.

Description of the Change: Remove hard coded python version from lit tests.

Benefits: Users / developers will be able to run lit tests with other python versions.

Possible Drawbacks: None?

Related GitHub Issues:

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[paul0403]

Does this mean all the "test wheels (python3.*) / frontend lit tests" have always been just 3.10? 😨

[erick-xanadu]

@paul0403 maybe not, I think this is the default. Maybe the alternative is to configure the variable, but for some reason it didn't set. Let me keep this as a draft for now before merging.

[dime10]

I think if you launch them through CMake, which the lit and test-frontend make targets do, the value for the executable is obtained from the CMake configuration. The fallback, if launching directly from the terminal via lit frontend/test/lit would be the python3.10 value.

The config is mapping the variable here:

catalyst/mlir/test/frontend/lit.site.cfg.py.in

Line 4 in 8c9189b

config.python_executable = "@Python3_EXECUTABLE@"

[dime10]

We can choose whatever we think is most appropriate as a fallback, probably python3? I think some systems don't define python if only Python 3 is installed, which can be annoying.