Improve architecture guessing

Right now, the "architecture guessing" is quite unreliable. The latest attempts to improve the situation worsened the situation even.

We should rework it entirely. My proposal is to keep looking for all executable files and `.so*` library files. We check whether they are ELF files, then parse their architecture out. @azubieta had prepared some code somewhere for this purpose.

In case there's multiple architectures in the list, instead of having to ask the user we could try a "majority" approach. For instance, if there's an absolute majority, we pick that (we could even use a 2/3 or 3/4 majority approach to make it even more reliable). If we cannot guess it that way, we can at least show the user "these are the ones we found, please pick one by doing XYZ".