util/lint & LICENSES: Add GCC-exception-3.1 to license exceptions

The gcov files in the lib directory are licensed GPL 3.0 with the GCC
runtime library exception.

Add this as a valid license so that the files can get a correct SPDX
identifier.

Signed-off-by: Martin Roth <martin.roth@amd.corp-partner.google.com>
Change-Id: I1cf9c3125592741923c9b4481038055f24fe6ab1
Reviewed-on: https://review.coreboot.org/c/coreboot/+/66495
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>

0 files changed, 0 insertions, 0 deletions