meta/lib/oe/sbom30.py: set alias for scan declared licenses

meta/lib/oe/sbom30.py: set alias for scan declared licenses

when using SPDX_INCLUDE_SOURCES, it calls scan_declared_licenses
to scan licenses from source file, set alias for the newly added
license and and license alias to hasDeclaredLicense relationship

$ echo 'MACHINE = "qemux86-64"' >> conf/local.conf
$ echo 'SPDX_INCLUDE_SOURCES = "1"' >> conf/local.conf
$ bitbake shadow
$ vim tmp/deploy/spdx/3.0.1/corei7-64/recipes/recipe-shadow.spdx.json
Before this commit
...
    {
      "type": "Relationship",
      ...
      "from": "http://spdx.org/spdxdocs/shadow-10e66933-65cf-5a2d-9a1d-99b12a405441/d0cdb0d02e54d55e52fccf8631f8290b161ad43fe31fffe09e8e25041d2280cf/sourcefile/11048",
      "relationshipType": "hasDeclaredLicense",
      "to": [
        "http://spdx.org/spdxdocs/shadow-10e66933-65cf-5a2d-9a1d-99b12a405441/d0cdb0d02e54d55e52fccf8631f8290b161ad43fe31fffe09e8e25041d2280cf/license/3_24_0/BSD-3-Clause",
      ]
    },
...

After this commit
...
    {
      "type": "Relationship",
      ...
      "from": "http://spdx.org/spdxdocs/shadow-10e66933-65cf-5a2d-9a1d-99b12a405441/d0cdb0d02e54d55e52fccf8631f8290b161ad43fe31fffe09e8e25041d2280cf/sourcefile/11048",
      "relationshipType": "hasDeclaredLicense",
      "to": [
        "http://spdxdocs.org/openembedded-alias/by-doc-hash/cc72db638e3f8e283e722af0ecc77d19f93cc6736700ee76477e3773b6b07b05/shadow/UNIHASH/license/3_24_0/BSD-3-Clause"
      ]
    },
...

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>