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>

go/export.cc

diff --git a/go/export.cc b/go/export.cc
index b27d2fa..277aa74 100644
--- a/go/export.cc
+++ b/go/export.cc
@@ -1231,7 +1231,7 @@
   if (name.empty())
     this->write_c_string("?");
   else
-    this->write_string(Gogo::message_name(name));
+    this->write_string(Gogo::unpack_hidden_name(name));
 }
 
 // Write an integer value to the export stream.