classes: sign-efi: allow to configure deployment directory

This is needed for systems that build and deploy two different linux
kernels like is the case when using the balena bootloader so that
different recipes do not try to deploy the same files.

Change-type: patch
Signed-off-by: Alex Gonzalez <alexg@balena.io>

meta-balena-common/classes/sign-efi.bbclass

@@ -1,5 +1,7 @@
 inherit deploy
 
+DESTDIR ?= "${DEPLOYDIR}"
+
 # Do not run on native recipes
 do_sign_efi:class-native() {
     :
@@ -48,7 +50,7 @@ do_sign_efi () {
 do_deploy:append:class-target() {
     for SIGNING_ARTIFACT in ${SIGNING_ARTIFACTS}; do
         if [ -f "${SIGNING_ARTIFACT}.signed" ]; then
-            install -m 0644 "${SIGNING_ARTIFACT}.signed" "${DEPLOYDIR}/$(basename ${SIGNING_ARTIFACT})"
+            install -m 0644 "${SIGNING_ARTIFACT}.signed" "${DESTDIR}/$(basename ${SIGNING_ARTIFACT})"
         fi
     done
 }