internal/pkg: create symlinks for files

These are much easier to handle than hard links and should be just as transparent for this use case.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg.go

@@ -342,8 +342,8 @@ func (c *Cache) storeFile(
 		return err
 	}
 
-	return os.Link(
-		checksumPathname.String(),
+	return os.Symlink(
+		"../"+dirChecksum+"/"+path.Base(checksumPathname.String()),
 		identifierPathname.String(),
 	)
 }