Fix compiler error with msvc on non-unicode system

[xyz1001]

same as getsentry/crashpad#85

[codecov]

Codecov Report

Merging #846 (0bdf456) into master (6c76f58) will decrease coverage by 0.08%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #846      +/-   ##
==========================================
- Coverage   82.60%   82.53%   -0.08%     
==========================================
  Files          53       53              
  Lines        7352     7362      +10     
  Branches     1185     1186       +1     
==========================================
+ Hits         6073     6076       +3     
- Misses       1170     1176       +6     
- Partials      109      110       +1     

[supervacuus]

Thanks again @xyz1001. The same applies here with global flags vs. setting via target_compile_options(). There is an upcoming refactoring I'll have to do for the MSVC build, and I will change that there. Please add a changelog entry in the following form:

**Fixes**:

- Fix MSVC compiler error with on non-Unicode systems ([#846](https://github.com/getsentry/sentry-native/pull/846), [crashpad#85](https://github.com/getsentry/crashpad/pull/85))

in the ## Unreleased section. Thx.