Adjust build tags to allow building on tinygo; for #73.

Passes "tinygo test" on macos and linux. Passes cross test to windows from macos, i.e. "GOOS=windows tinygo test -c; wine64 go-isatty.test". Had to adjust the build tags on isatty_others.go to avoid multiple definition link failure on ``` $ GOOS=windows tinygo test ```