Esnure we detect semgrep's "unlicensed" SPDX tags

[pombredanne]

See https://github.com/semgrep/semgrep-rules/blob/f82ac940fd7372ba45c54a52fbbd341e676bcb5e/solidity/performance/use-nested-if.sol#L1

• // SPDX-License-Identifier: UNLICENSED

This looks like this comes from crypto currencies code using Solidity.

[alok1304]

It detects unknown-spdx license expression.

 "license_detections": [
    {
      "identifier": "unknown_spdx-07e37263-9fc9-896c-efc7-e27d7c9e585e",
      "license_expression": "unknown-spdx",
      "license_expression_spdx": "LicenseRef-scancode-unknown-spdx",
      "detection_count": 1,
      "reference_matches": [
        {
          "license_expression": "unknown-spdx",
          "license_expression_spdx": "LicenseRef-scancode-unknown-spdx",
          "from_file": "use-nested-if.sol",
          "start_line": 1,
          "end_line": 1,
          "matcher": "1-spdx-id",
          "score": 100.0,
          "matched_length": 4,
          "match_coverage": 100.0,
          "rule_relevance": 100,
          "rule_identifier": "spdx-license-identifier-unknown_spdx-b239a566f89d6d342e8628db86409053928aa77d",
          "rule_url": null
        }
      ]
    }
  ]