XNAP is asn1c compiled with -no-gen-BER. Correspondingly, no
ber_decoder.h file is created. However, when running cmake followed by
ninja, it notices the absence of this file:
ninja explain: output openair2/XNAP/MESSAGES/ber_decoder.h doesn't exist
which triggers a complete rebuild of XNAP ASN.1. Without this file, the
targets are not marked as dirty.