bugfix: don't crash when c++filt is not available in the toolchain

[sarfata]

The PIC xc16 toolchain does not include any c++ tools and puncover crashed while trying to open the elf file. This fixes it.

[HBehrens]

This one should still work once rebased and a unit-test exists, right @sarfata ?

[sarfata]

Yes this should still work. This was just blocked by CI issues.

[HBehrens]

Cool, are you willing to rebase + provide a test that shows the behavior?

[codecov]

Codecov Report

Merging #24 into master will decrease coverage by 0.07%.
The diff coverage is 60.00%.

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
- Coverage   74.49%   74.42%   -0.08%     
==========================================
  Files          17       17              
  Lines        1345     1349       +4     
==========================================
+ Hits         1002     1004       +2     
- Misses        343      345       +2     

Impacted Files	Coverage Δ
puncover/gcc_tools.py	65.62% <60.00%> (-2.24%)	⬇️

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[sarfata]

I have rebased.

Making an integration test for this would require the xc16 toolchain from Microchip which has a complicated license (user has to download it from their website - cant bundle it). It also seems like a lot of efforts for a pretty simple change.

Overall, I am not sure this PR is really that useful since even with this fix, puncover did not work well with the elf files generated by this compiler (cf #26). For other toolchains built on GCC, I am guessing cppfilt will always be available.

Maybe we just close without merging and if someone picks up #26, this fix will be visible and can be bundled in.

[HBehrens]

Ok, will close then. Thank you for your work and perspective, @sarfata !