go/internal/gcimporter: fix IImportBundle error text

When called from IImportBundle, the current code returns
a message saying:

	cannot import "" (actual error) ...

That looks like the user has somehow caused an invalid import path
to be passed, which is not the case. Skip the wrapping in the bundle case.

Change-Id: I6cdb83911d18501895671fc70d87c2519f0570a3
Reviewed-on: https://go-review.googlesource.com/c/tools/+/310514
Trust: Russ Cox <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Austin Clements <[email protected]>
Auto-Submit: Russ Cox <[email protected]>
gopls-CI: kokoro <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: rsc

go/internal/gcimporter/iimport.go

@@ -100,7 +100,9 @@ func iimportCommon(fset *token.FileSet, imports map[string]*types.Package, data
 	if !debug {
 		defer func() {
 			if e := recover(); e != nil {
-				if version > currentVersion {
+				if bundle {
+					err = fmt.Errorf("%v", e)
+				} else if version > currentVersion {
 					err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
 				} else {
 					err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)