Improve Version format compile error

[nickcernis]

• Helps users identify the only legal Version format string ({}) more quickly.
• Better matches other compile errors like those in lib/std/zig/fmt.zig:

zig/lib/std/zig/fmt.zig

Lines 68 to 77 in a65ba6c

	@compileError("expected {} or {'}, found {" ++ fmt ++ "}");
	}
	},
	'\'' => {
	if (fmt.len == 1 and fmt[0] == '\'') {
	try writer.writeAll("\\'");
	} else if (fmt.len == 0) {
	try writer.writeByte('\'');
	} else {
	@compileError("expected {} or {'}, found {" ++ fmt ++ "}");

To reproduce the compile error

const std = @import("std");
const builtin = @import("builtin");

pub fn main() !void {
    std.debug.print("{s}", .{builtin.zig_version});
}

Error Before	Error After
error: Unknown format string: 's'	error: expected {}, found {s}

[Vexu]

lib/std/fmt.zig has a nice function for this error that it uses everywhere invalidFmtErr. I think a nicer solution would be making it public and changing all the custom formatters in the std lib to use it.

[nickcernis]

Thanks for the suggestion, @Vexu — I opened #13526 to replace this.