unix: Fix mkerrors.sh to do comparison correctly
unix: Fix mkerrors.sh to do comparison correctly

Bash should use "=" not "-eq" for equality comparison.

Some incorrect comparison operators were missed in:
https://go-review.googlesource.com/c/sys/+/41832

Change-Id: I110968287b7370870301b2fdd2a4ec188f623a39
Reviewed-on: https://go-review.googlesource.com/61770
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/sys,multiplay/golang-sys,multiplay/golang-sys,golang/sys,golang/sys,multiplay/golang-sys,multiplay/golang-sys