compiler: don't localize names in export data

Localizing names in export data causes the compiler output to change
depending on the LANG environment variable, so don't do it.

Change-Id: Icf1f867656e39d24dc1e92e51a2bc45bbbcda05b
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/214038
Reviewed-by: Cherry Zhang <cherryyz@google.com>