go/gcexportdata: make test portable to MS Windows

Fixes issue #17565

Change-Id: I67d2e11acae873ac47694a73ced40d2db38c0fc0
Reviewed-on: https://go-review.googlesource.com/31813
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/go/gcexportdata/example_test.go b/go/gcexportdata/example_test.go
index d16d712..2472706 100644
--- a/go/gcexportdata/example_test.go
+++ b/go/gcexportdata/example_test.go
@@ -51,7 +51,8 @@
 	fmt.Printf("Package members:    %s...\n", pkg.Scope().Names()[:5])
 	println := pkg.Scope().Lookup("Println")
 	posn := fset.Position(println.Pos())
-	posn.Line = 123 // make example deterministic
+	posn.Line = 123                                 // make example deterministic
+	posn.Filename = filepath.ToSlash(posn.Filename) // make example deterministic
 	fmt.Printf("Println type:       %s\n", println.Type())
 	fmt.Printf("Println location:   %s\n", posn)