term: fix build on js/wasm and nacl
term: fix build on js/wasm and nacl

Change-Id: I8ff21952a72f3f5838c9959f00d9f4c8b4b45d2d
Reviewed-on: https://go-review.googlesource.com/c/term/+/201117
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/term