fix(windows): handle invalid utf16le in command line arguments (#11612)

src/string_builder.zig

@@ -48,20 +48,29 @@ pub fn count16(this: *StringBuilder, slice: []const u16) void {
 }
 
 pub fn count16Z(this: *StringBuilder, slice: [:0]const u16) void {
-    const result = bun.simdutf.length.utf8.from.utf16.le(slice);
+    const result = bun.strings.elementLengthUTF16IntoUTF8([:0]const u16, slice);
     this.cap += result + 1;
 }
 
-pub fn append16(this: *StringBuilder, slice: []const u16) ?[:0]u8 {
+pub fn append16(this: *StringBuilder, slice: []const u16, fallback_allocator: std.mem.Allocator) ?[:0]u8 {
     var buf = this.writable();
+    if (slice.len == 0) {
+        buf[0] = 0;
+        this.len += 1;
+        return buf[0..0 :0];
+    }
+
     const result = bun.simdutf.convert.utf16.to.utf8.with_errors.le(slice, buf);
     if (result.status == .success) {
         this.len += result.count + 1;
         buf[result.count] = 0;
         return buf[0..result.count :0];
+    } else {
+        var list = std.ArrayList(u8).init(fallback_allocator);
+        var out = bun.strings.toUTF8ListWithTypeBun(&list, []const u16, slice) catch return null;
+        out.append(0) catch return null;
+        return list.items[0 .. list.items.len - 1 :0];
     }
-
-    return null;
 }
 
 pub fn appendZ(this: *StringBuilder, slice: string) [:0]const u8 {