POSIX shell now supports $((expression)) for arithmetic expression evaluation. This removes the need for an external command, which may not be available on the build host. Change-Id: Ibd1342c723c2320d77c4de5b1620be32086daa56 Reviewed-on: https://review.haiku-os.org/c/haiku/+/9238 Reviewed-by: Adrien Destugues <[email protected]> Tested-by: Commit checker robot <[email protected]>