cros_start_vm: Pass board name to start_kvm

We need to know what kind of hardware we're virtualizing. Pass the value
of the --board flag to start_kvm so that we can configure an appropriate
virtual CPU.

BUG=chromium:484307
TEST=cros_start_vm --board x86-alex_freon
CQ-DEPEND=CL:269405

Change-Id: Ia5b64a5831074ada48c289504e3fff99b126ca5a
Reviewed-on: https://chromium-review.googlesource.com/269397
Reviewed-by: David James <davidjames@chromium.org>
Reviewed-by: Prathmesh Prabhu <pprabhu@chromium.org>
Trybot-Ready: David James <davidjames@chromium.org>
Trybot-Ready: Michael Spang <spang@chromium.org>
Tested-by: Michael Spang <spang@chromium.org>
Commit-Queue: David James <davidjames@chromium.org>
diff --git a/host/cros_start_vm b/host/cros_start_vm
index 0e2a5e3..64fe5ec 100755
--- a/host/cros_start_vm
+++ b/host/cros_start_vm
@@ -37,6 +37,6 @@
 
 [ -e "${FLAGS_image_path}" ] || die "Image ${FLAGS_image_path} does not exist."
 
-start_kvm "${FLAGS_image_path}"
+start_kvm "${FLAGS_image_path}" "${FLAGS_board}"
 
 echo "ssh root@${HOSTNAME} -p ${FLAGS_ssh_port} -o StrictHostKeyChecking=no"