cmake: Set minimum required Zephyr SDK version to 0.13.1

This commit sets the minimum required Zephyr SDK version to 0.13.1,
which fixes the following critical issues:

1. Xtensa initial malloc failure (GitHub issue #38258)
2. ARMv8-M security extension vulnerability (CVE-2021-35465)

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
1 file changed