This ensures that gdb tests run on Windows by ignoring any line ending.

Works with gdb 7.7, however with gdb 7.9 and 7.12 gets an error
error:

    internal-error: buildsym_init: Assertion `free_pendings == NULL'
    failed.

Updates #21380

Change-Id: I6a6e5b2a1b5efdca4dfce009fcb9c134c87497d6
Reviewed-on: https://go-review.googlesource.com/102419
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>