`RULE-5-8`: Consider linkage when determining conflicting declarations

### Affected rules
 - `RULE-5-8`

### Description

CodeQL databases can be created which include multiple libraries or binaries which are not intended to be linked together. This includes cases where the same library is built for multiple platforms. In these cases it is reasonable not to report declarations with the same name as "conflicting", by inspecting the linkage information in the database.