Rewrite test6952 to be independent of the CC variable

[Geod24]

This was an issue on other platforms, as CC might be gcc, cc,
clang, sometimes even c++, g++ or clang++.
Instead of dealing with that, just provide our own wrapper script
which writes the arguments passed to it, and voila.

[dlang-bot]

Thanks for your pull request, @Geod24!

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Testing this PR locally

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dub run digger -- build "master + dmd#11053"

[lionello]

The compiler always prints the value of CC so couldn't we instead just look for that value?

[Geod24]

We could, but depending on whatever's in the environment is quite brittle IMO. You experienced it yourself: changes to CC can be done from the calling Makefiles to affect other tests, and will mistakenly affect this one as well.

Additionally, the output of -v isn't what one can consider a stable API. What if one day someone decides to output all the environment variables that affect compilation (for easily-reproducible build) ? IMO removing the part that can change from the equation is much more robust long term.