feature: add sgx_tracer with memcmp example

[Charitonos]

New feature

tracer support for sgx-step

[jovanbulck]

Thanks a lot @Charitonos , this is very nice! See (detailed, sometimes nitpicky) comments above

For the first review iteration, I suggest we try to:

• focus on finalizing the tracer API (see comments on the init and opt_add functions):
  • first always have to do sgx_tracer_add_mod
  • then optionally call sgxs_tracer_init_mod to pass options?
• avoid the code duplication from copying the entire memcmp example: can we just create a minimal standalone main.c that traces everything for a small enclave? (Once this gets merged, I think we can focus on creating a unified cmdline-driven main.c sgx-step cmdline utility that could work for any enclave :) )

[jovanbulck]

Many thanks @Charitonos ! I tested it on the aeolus machine (using sim-stepping) and it works nicely there :) There's only a couple of very minor nitpicks/clarifications left before this can be merged! 👍

[jovanbulck]

Thanks @Charitonos , looks excellent!

Before I can merge this, I want to avoid any licensing issues in the upstream source tree: can you please copy the LICENCE file from https://github.com/zyantific/zydis into tools/disasm/zydis-amalgamated-v4.0.0/LICENSE and add a README.md in tools/disasm/README.md to explain the zydis-amalgamated-v4.0.0 is taken verbatim from https://github.com/zyantific/zydis and is licensed under MIT license? 🙏

Once this is done, it can be merged! 🚀

[jovanbulck]

Merged, thanks @Charitonos ! 🚀