🐛Binary-Artifacts: no longer fall back to file extensions

[evverx]

Looks like isArchive is supposed to cover all the filetypes
the Binary-Artifacts check is interested in:
https://github.com/h2non/filetype#archive. If types like dll
aren't supported they probably should be added to the matchers
library (by the way there is an in-flight PR trying to
achieve exactly that: h2non/filetype#103)

With this patch applied scorecard no longer complains about
systemd:

    {
      "details": null,
      "score": 10,
      "reason": "no binaries found in the repo",
      "name": "Binary-Artifacts",
      "documentation": {
        "url": "https://github.com/ossf/scorecard/blob/63e3b92466f0403159c02f1ccedd43f9400e8b26/docs/checks.md#binary-artifacts",
        "short": "Determines if the project has generated executable (binary) artifacts in the source repository."
      }

and still can successfuly flag repositories with suspicious
elf files for example

./scorecard --verbosity Debug  --show-details --format json  --repo=https://github.com/evverx/binary-artifacts-test --checks Binary-Artifacts | jq | tee OUT
{
  "repo": {
    "name": "github.com/evverx/binary-artifacts-test",
    "commit": "11cbc0fddac398f346639b0552061f859e506b02"
  },
...
  "score": 0.0,
  "checks": [
    {
      "details": [
        "Warn: binary detected: date",
        "Warn: binary detected: nothing-to-see-here-hehe.txt"
      ],
      "score": 0,
      "reason": "binaries present in source code",
      "name": "Binary-Artifacts",
...

[evverx]

If the check shouldn't flag pdf files for example I think it would make sense to replace this part with something like

kind, _ := filetype.Archive(content)
if !stopList[kind.Extension] {
...
}

where stopList contains pdf

[evverx]

To get this to work more or less reliably I think some kind of h2non/filetype#73 should be implemented first. I guess I'm back where I started :-)