[9.18] chg: ci: Fail when spatch can't process source code

Sometimes spatch fails to process the source code:

    EXN: Failure("replacement: node 80: {7[1,2,30,31,32] in isc__nm_base64_to_base64url reachable by inconsistent control-flow paths") in ./lib/isc/netmgr/http.c

Closes #5567

Backport of MR !11115

Merge branch 'backport-5567-spatch-detect-more-error-conditions-9.18' into 'bind-9.18'

See merge request isc-projects/bind9!11134