Cast to `*const c_char` instead of `*const i8`

[Gor027]

Fixes build error on many processors for which c_char is an alias for unsigned such as ARM, aarch64, hexagon, etc.

Pre-review checklist

• [x] I have split my patch into logically separate commits.
• [x] All commit messages clearly explain what they change and why.
• [x] PR description sums up the changes and reasons why they should be introduced.
• [ ] I have enabled appropriate tests in .github/workflows/build.yml in gtest_filter.
• [ ] I have enabled appropriate tests in .github/workflows/cassandra.yml in gtest_filter.