Detect jemalloc and do not proceed if used

In Knot Resolver, we use jemalloc when possible, because it behaves slightly better with our particular memory allocation patterns. This is at odds with Deckard testing, because it uses libfaketime, which exhibits issues when used in conjunction with jemalloc.

From time to time, this causes confusion on our side when we try to test a jemalloc-linked Knot Resolver with Deckard.

It would be a nice-to-have feature of Deckard, if it could detect that any of the tested servers is dynamically linked against libjemalloc, printed a warning stating so, and skipped the test (exited with code 77 - meson context). There should also be an option added to force-run the test, in case a new version of libfaketime comes out that does not exhibit the issue anymore.

Further info:

• ldd is a command which can print an executable's dependencies, readily available on most *nix-like OSes, but be careful about running it on untrusted stuff.
• libtree is a nice alternative to ldd, which should not exhibit its security issues.
• LIEF seems to be a maintained Python library which can parse ELF files, i.e. get (at least some of) the information ldd and/or libtree get in the form of a Python object.