%lL will prepend the current directory to the filename, which is not
what we want here (as the file name is already absolute).

Fixes #9150.

Change-Id: I4c9386be6baf421393b92d9401a264b4692986d0
Reviewed-on: https://go-review.googlesource.com/2231Reviewed-by: Ian Lance Taylor <iant@golang.org>