rootfs-builder: only look for AGENT_POLICY_FILE if AGENT_POLICY=yes

When the rootfs is built with AGENT_POLICY=no, the build fails at
line 36 for us, since our package build does not have access to the
entire source at once. Rather, we only copy the directories that we
think we'll need (and we missed that one). TBA in a future packaging
change. Upstream isn't affected as they build with the whole code base.

Signed-off-by: Aurelien Bombo <abombo@microsoft.com>

tools/osbuilder/rootfs-builder/rootfs.sh

@@ -33,7 +33,7 @@ AGENT_POLICY_FILE=${AGENT_POLICY_FILE:-"allow-all.rego"}
 lib_file="${script_dir}/../scripts/lib.sh"
 source "$lib_file"
 
-agent_policy_file="$(readlink -f "${script_dir}/../../../src/kata-opa/${AGENT_POLICY_FILE}")"
+[ "${AGENT_POLICY}" == "yes" ] && agent_policy_file="$(readlink -f "${script_dir}/../../../src/kata-opa/${AGENT_POLICY_FILE}")"
 
 #For cross build
 CROSS_BUILD=${CROSS_BUILD:-false}
@@ -330,7 +330,7 @@ check_env_variables()
 
 	[ -n "${KERNEL_MODULES_DIR}" ] && [ ! -d "${KERNEL_MODULES_DIR}" ] && die "KERNEL_MODULES_DIR defined but is not an existing directory"
 
-	[ ! -f "${agent_policy_file}" ] && die "agent policy file not found in '${agent_policy_file}'"
+	[ "${AGENT_POLICY}" == "yes" ] && [ ! -f "${agent_policy_file}" ] && die "agent policy file not found in '${agent_policy_file}'"
 
 	[ -n "${OSBUILDER_VERSION}" ] || die "need osbuilder version"
 }