windows: avoid the use of wcwidth

src/benchmark/CodepointWidth.zig

@@ -6,6 +6,7 @@
 const CodepointWidth = @This();
 
 const std = @import("std");
+const builtin = @import("builtin");
 const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const Benchmark = @import("Benchmark.zig");
@@ -104,6 +105,11 @@ fn stepNoop(ptr: *anyopaque) Benchmark.Error!void {
 extern "c" fn wcwidth(c: u32) c_int;
 
 fn stepWcwidth(ptr: *anyopaque) Benchmark.Error!void {
+    if (comptime builtin.os.tag == .windows) {
+        log.warn("wcwidth is not available on Windows", .{});
+        return;
+    }
+
     const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
 
     const f = self.data_f orelse return;