std.Target: Add a function for determining char signedess

Copied from arocc https://github.com/Vexu/arocc/blob/c1955a474270562a4640217e62c888b52c79d39e/src/target.zig#L7
657fe55711Evan Haas committed on 6/20/2023, 7:26:40 AMparenta72d634
1 file changedLine totals unavailable