Correctly compute_normalized_license for alpine

* The license of Alpine installed system packages was not detected
  correctly. It now uses the Alpine specific procedure.

Reference: aboutcode-org/scancode.io#478
Signed-off-by: Philippe Ombredanne <[email protected]>

Author: pombredanne

src/packagedcode/alpine.py

@@ -58,6 +58,11 @@ def parse(cls, location):
             package_type=cls.default_package_type,
         )
 
+    @classmethod
+    def compute_normalized_license(cls, package):
+        _declared, detected = detect_declared_license(package.declared_license)
+        return detected
+
     @classmethod
     def assemble(cls, package_data, resource, codebase):
         # get the root resource of the rootfs
@@ -76,6 +81,7 @@ def assemble(cls, package_data, resource, codebase):
 
         package.license_expression = cls.compute_normalized_license(package)
 
+
         dependent_packages = package_data.dependencies
         if dependent_packages:
             yield from models.Dependency.from_dependent_packages(