improve the cache hash logic for c objects with respect to extra flags and file parameters

[andrewrk]

zig/src/Compilation.zig

Lines 1505 to 1520 in ab7ea53

	{
	// Hash the extra flags, with special care to call addFile for file parameters.
	// TODO this logic can likely be improved by utilizing clang_options_data.zig.
	const file_args = [_][]const u8{"-include"};
	var arg_i: usize = 0;
	while (arg_i < c_object.src.extra_flags.len) : (arg_i += 1) {
	const arg = c_object.src.extra_flags[arg_i];
	man.hash.addBytes(arg);
	for (file_args) |file_arg| {
	if (mem.eql(u8, file_arg, arg) and arg_i + 1 < c_object.src.extra_flags.len) {
	arg_i += 1;
	_ = try man.addFile(c_object.src.extra_flags[arg_i], null);
	}
	}
	}
	}