Use system call to retrieve the Linux kernel version

[tshakalekholoane]

Replace the following with a system call.

bat/internal/cli/cli.go

Lines 199 to 206 in 9dc3af6

	func kernel() (string, error) {
	cmd := exec.Command("uname", "--kernel-release")
	out, err := cmd.Output()
	if err != nil {
	return "", err
	}
	return string(out), nil
	}