Support executing random programs (!)

zig/sdl/hello_sdl.zig

    else if (std.mem.startsWith(u8, cmd, "man "))
        // TODO: handle `man 5 sway`
        &[_][]const u8{ "man", cmd["man ".len..] }
    else if (cmd.len > 0 and std.ascii.isDigit(cmd[0]))
        &[_][]const u8{ "/usr/bin/qalc", "-terse", cmd }
    else
        &[_][]const u8{ "/usr/bin/qalc", "-terse", cmd };
        &[_][]const u8{ "bash", "-c", cmd };
    for (argv) |arg| {
        std.debug.print("'{s}' ", .{arg});
    }