Support built-ins necessary for networking driver verification

[jprotopopov-ut]

net subsystem of the Linux kernel relies on certain built-ins (e.g. bswap) that are not currently supported by Goblint. For instance, include/net/inet_ecn.h file contains these. The goal would be to implement support for these built-ins, enabling the analysis of networking drivers.

Currently, the extent of missing implementation is not known, so aforementioned bswap should only be treated as a starting point in further investigation. Thus, as part of this task, some (even if trivial) environment models necessarily will need to be composed.

[jprotopopov-ut]

The current issue can be replicated via

./driver.py  --db ~/kernel/linux-6.14.9.db --goblint ~/goblint/analyzer/goblint --harness-compiler $PWD/rh_generator.sh rh_examples/ipv6_exthdrs.json

You can ignore failures reported by LTSmin at the beginning and focus on GoblintCil__Errormsg.Error errors later in the log