Normalize manifest zip path in release helper

Author: AnastaZIuk

cmake/NablaAssetManifestsPrepareRelease.cmake

@@ -20,6 +20,9 @@ endif()
 get_filename_component(SOURCE_ROOT "${SOURCE_ROOT}" ABSOLUTE)
 get_filename_component(PAYLOAD_ROOT "${PAYLOAD_ROOT}" ABSOLUTE)
 get_filename_component(MANIFEST_ROOT "${MANIFEST_ROOT}" ABSOLUTE)
+if(DEFINED MANIFESTS_ZIP AND NOT "${MANIFESTS_ZIP}" STREQUAL "")
+    get_filename_component(MANIFESTS_ZIP "${MANIFESTS_ZIP}" ABSOLUTE)
+endif()
 set(_channel_manifest_root "${MANIFEST_ROOT}/${CHANNEL}")
 
 if(NOT EXISTS "${SOURCE_ROOT}")