WSL Optimisations and Bugfixes for CI

[andrjohns]

Submission Checklist

• Run unit tests
• Declare copyright holder and agree to license (see below)

Summary

This PR includes a number of small optimisations and bugfixes to the WSL backend

Copyright and Licensing

Please list the copyright holder for the work you are submitting
(this will be you or your assignee, such as a university or company):
Andrew Johnson

By submitting this pull request, the copyright holder is agreeing to
license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[codecov-commenter]

Codecov Report

Merging #711 (cb9ce8f) into master (09a9be2) will decrease coverage by 0.12%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master     #711      +/-   ##
==========================================
- Coverage   88.46%   88.33%   -0.13%     
==========================================
  Files          12       12              
  Lines        4023     4030       +7     
==========================================
+ Hits         3559     3560       +1     
- Misses        464      470       +6     

Impacted Files	Coverage Δ
R/model.R	90.49% <0.00%> (-0.13%)	⬇️
R/run.R	94.40% <0.00%> (-0.15%)	⬇️
R/csv.R	96.44% <14.28%> (-1.23%)	⬇️
R/utils.R	73.84% <100.00%> (+0.32%)	⬆️

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[andrjohns]

Nice to finally see all of the test results in green again!

[andrjohns]

And before I forget - if you do release notes or similar for the next release, it would be good to mention that the new model methods (log_prob etc) and exposing UDF features aren't WSL-compatible just yet (since the cmdstan libraries for the TBB and Sundials are built under linux so R can't link to them under Windows)

[rok-cesnovar]

Will do! Thanks a ton, @andrjohns! This looks great, nice to have the green back :)