Fix clang -Wabsolute-value warning + Trigger linux clang build on clang in branch name

[kazarmy]

Your checklist for this pull request

• I've read the guidelines for contributing to this repository
• I made sure to follow the project's coding style
• I've documented or updated the documentation of every function and struct this PR changes. If not so I've explained why.
• I've added tests that prove my fix is effective or that my feature works (if possible)
• I've updated the rizin book with the relevant information (if needed)

Detailed description

This pr fixes the following warning on the linux-meson-clang-tests build:

(https://github.com/rizinorg/rizin/runs/4342000656?check_suite_focus=true#step:12:553)

Test plan

All builds are green. The linux-meson-clang-tests build runs on this pr. The above warning is no longer emitted.

Closing issues

...

pr has changed significantly