dynamic linkage checks

[errordeveloper]

It would be great to be able to check linkage.
It's currently possible with commandTests, but only if ldd is present (often not the case for minimal images) and it requires matching the output, which can be tricky to actually implement.

Example:

elfBinaryTests:
- name: "bash is dynamically linked"
   path: "/bin/bash"
   noMissingLibs: true
   libraries:
   - "linux-vdso.so.1"
   - "libtinfo.so.6"
   -  "libdl.so.*"
   - "libc.so.6"
   - "ld-linux-*.so.*"

[nkubala]

@errordeveloper another reasonable request after #257! I'd be happy to accept a contribution for this if you're interested.

could we consolidate noMissingLibs and libraries and just have a list of requiredLibraries? I suppose we might also want to check for optional ones but just a thought.