fix(armhf): Fix armhf kernel file detection

Armhf images install the `generic-lpae` kernel, while other ARCHes use the
standard `generic` kernel when building the "virtual" image flavour.
Code was looking for a kernel binary ending with -generic in armhf
builds, and failed. Add a special condition to handle armhf builds'
kernel ending with `generic-lpae`

References:
[1] https://bugs.launchpad.net/cloud-images/+bug/2029527

live-build/auto/build

@@ -618,7 +618,11 @@ for FLAVOUR in $LB_LINUX_FLAVOURS; do
 	fi
 	case $FLAVOUR in
 		allwinner|virtual|generic-hwe-*)
+			if [ "$ARCH" = "armhf" ]; then
+				FLAVOUR="generic-lpae"
+			else
 				FLAVOUR="generic"
+			fi
 			;;
 		oem-*)
 			FLAVOUR="oem"