Revert "x86: Allow generating user-space headers without a compiler"

This reverts commit 829fe4aa.

This change builds on top of another change which we are reverting.
Revert it too, to avoid a conflict.

Bug: 120440614
Change-Id: I23fd0ebda98eb2646efdcfdfa06bb6ab627ba471
Signed-off-by: Alistair Strachan <astrachan@google.com>