xtensa-build-zephyr: add imx8 platform

Add imx8 platform for local testing.

TODO: Update xtensa-build-zephyr.sh when Zephyr repo
is updated with imx8 support.

Signed-off-by: Iuliana Prodan <iuliana.prodan@nxp.com>

Author: iuliana-prodan

scripts/xtensa-build-zephyr.sh

@@ -114,6 +114,10 @@ build()
 				PLAT_CONFIG='intel_adsp_cavs25'
 				RIMAGE_KEY=modules/audio/sof/keys/otc_private_key_3k.pem
 				;;
+			imx8)
+				PLAT_CONFIG='nxp_adsp_imx8'
+				RIMAGE_KEY='' # no key needed for imx8
+				;;
 			*)
 				echo "Unsupported platform: $platform"
 				exit 1