Add in missing build contraint

Author: Jacalz

src/mime/type_unix_test.go

@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
+//go:build aix || darwin || dragonfly || freebsd || (js && wasm) || linux || netbsd || openbsd || solaris
+// +build aix darwin dragonfly freebsd js,wasm linux netbsd openbsd solaris
+
 package mime
 
 import (