bind: pin go/types to not produce types.Alias types

Bind currently targets the earlier go/types semantics (gotypesalias=0),
and needs to be updated to be compatible with the new (gotypesalias=1).

This is the only way in which the module isn't compatible with Go 1.23
language semantics, so add an explicit godebug line for it with a TODO.
This unblocks moving the module to Go 1.23 (as done in the next CL).

For golang/go#70698.

Change-Id: I59a61defdcf327aed9ccd67b123b1516cd118d9e
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/649381
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Hajime Hoshi <hajimehoshi@gmail.com>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>

go.mod

@@ -2,6 +2,19 @@ module golang.org/x/mobile
 
 go 1.22.0
 
+// The modern go/types type checker produces types.Alias
+// types for the explicit representation of type aliases.
+// (Initial opt-in support for it was added in Go 1.22,
+// and it became the default behavior in Go 1.23.)
+//
+// TODO(go.dev/issue/70698): Update the golang.org/x/mobile/bind
+// code generator for the new behavior and delete this temporary¹
+// forced pre-1.23 go/types behavior.
+//
+// ¹ It's temporary because this godebug setting will be removed
+//   in a future Go release.
+godebug gotypesalias=0
+
 require (
 	golang.org/x/exp/shiny v0.0.0-20230817173708-d852ddb80c63
 	golang.org/x/image v0.24.0