* sys: Make ImHex compile with -Wall -Wextra -Werror
* sys: Fixed various build errors on Linux
* sys: Explicitly ignore return value of `system` function
* sys: More fixes for the warnings GitHub Actions enables somehow
* sys: More fixes
* sys: Remove -Werror again to see all GitHub Actions warnings
* sys: Hopefully fixed all remaining warnings
* sys: Added back -Werror
* git: Change windows icon in GitHub Actions
