Use kvm kernel flavor for minimized cloud image, not virtual

debian/changelog

@@ -44,6 +44,7 @@ livecd-rootfs (2.408.19) UNRELEASED; urgency=medium
   [ Steve Langasek ]
   * debian/tests/default-bootstraps: minor adjustments to shell syntax,
     syncing with artful where this originated.
+  * Use kvm kernel flavor for minimized cloud image, not virtual
 
  -- Balint Reczey <rbalint@ubuntu.com>  Tue, 03 Oct 2017 17:35:04 +0200
 

live-build/auto/config

@@ -502,14 +502,28 @@ case $PROJECT in
 		if [ "${SUBPROJECT:-}" = minimized ]; then
 			add_task install cloud-image
 			add_package install sudo
+			# linux-kvm currently only exists in xenial, not in
+			# non-LTS suites.  Fall back to virtual flavor, which
+			# may or may not boot initramfsless but enables us to
+			# test building and possibly build derivative images
+			# using other kernel flavors.
+			# If you enable an extra ppa, it is assumed that
+			# linux-kvm is available since you control the
+			# archive and can provide this metapackage as
+			# necessary.
+			if [ -z "$EXTRA_PPAS" ] && [ "$SUITE" != xenial ]; then
+				KERNEL_FLAVOURS=virtual
+			else
+				KERNEL_FLAVOURS=kvm
+			fi
 		else
 			add_task install minimal standard cloud-image
 			add_package install ubuntu-minimal
+			KERNEL_FLAVOURS=virtual
 		fi
 
 		BINARY_REMOVE_LINUX=false
 		OPTS="${OPTS:+$OPTS }--initramfs=none"
-		KERNEL_FLAVOURS=virtual
 		case $ARCH in
 			armhf)
 				KERNEL_FLAVOURS=generic-lpae