[basic-cwe-examples] use size_t for a more definite error in 64-bit machdep

1 job for master in 40 minutes and 18 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Test
failed build #382163
docker

00:40:18

 
Name Stage Failure
failed
build Test
  Please report as 'crash' at https://git.frama-c.com/pub/frama-c/issues
Your Frama-C version is 22.0+dev (Titanium).
Note that a version and a backtrace alone often do not contain enough
information to understand the bug. Guidelines for reporting bugs are at:
https://git.frama-c.com/pub/frama-c/-/wikis/Guidelines-for-reporting-bugs
make[1]: Leaving directory '/builds/pub/open-source-case-studies/chrony/.frama-c'
make[1]: *** [../../Makefile.common:9: chrony-ntp-core.sarif] Error 4
make: *** [Makefile:118: chrony.sarif] Error 2
ERROR: Job failed: exit code 1