Draft: Makefile: fix target regenerating dune.inc

Context

The target supposed to regenerate dune.inc upon changes to TEZOS_PROTOCOL is seemingly broken. The first reason is that in src/lib_protocol_compiler/dune_protocol, the (include dune.inc) fails when a target becomes invalid (which typically happens when we remove or rename a file in lib_protocol). We fix this in the following way: in the Makefile, we remove the dune.inc and touch it. The next problem was that dune returns a non-zero exit code, hence the crafty || true.

Manually testing the MR

Add an .ml in lib_protocol and TEZOS_PROTOCOL, run make generate_dune, check that it compiles

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, the Development Version section of CHANGES.md for everything else).
• Select suitable reviewers using the Reviewers field below.