Add a kola verb

This is the first place we're wrapping mantle via our
main entrypoint, and hopefully we'll increase that.

For now we hardcode `-b rhcos`...but that should change.

Example usage: `coreos-assembler kola run rhcos.basic`.

Requires: coreos/mantle#920

src/cmd-kola

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+set -xeuo pipefail
+
+dn=$(dirname $0)
+. ${dn}/cmdlib.sh
+
+latest_qcow=$(get_latest_qcow)
+if [ -z "${latest_qcow}" ]; then
+    fatal "No latest build"
+fi
+
+exec sudo kola -b rhcos --tapfile test.tap --qemu-image ${latest_qcow} "$@"

src/cmd-run

@@ -7,6 +7,9 @@
 
 set -euo pipefail
 
+dn=$(dirname $0)
+. ${dn}/cmdlib.sh
+
 VM_DISK=
 VM_MEMORY=2048
 VM_PERSIST=0
@@ -71,10 +74,8 @@ while [ $# -ge 1 ]; do
 done
 
 if [ -z "${VM_DISK}" ]; then
-    if [ -L ./builds/latest ]; then
-        latest_build=$(readlink builds/latest)
-        VM_DISK=$(ls builds/${latest_build}/*-qemu.qcow2)
-    else
+    VM_DISK=$(get_latest_qcow)
+    if [ -z "${VM_DISK}" ]; then
         die "No builds/latest, and no -d argument provided"
     fi
 fi

src/cmdlib.sh

@@ -92,3 +92,16 @@ runcompose() {
          ${TREECOMPOSE_FLAGS:-} ${manifest} "$@"
     set +x
 }
+
+get_latest_build() {
+    if [ -L builds/latest ]; then
+        readlink builds/latest
+    fi
+}
+
+get_latest_qcow() {
+    local latest=$(get_latest_build)
+    if [ -n "$latest" ]; then
+        ls builds/${latest}/*-qemu.qcow2
+    fi
+}