configure: improve nettle, gmp, and hogweed soname detection

Some linkers might optimize away the libraries passed on the command line if they aren't actually needed, such as gnu ld with --as-needed. The ldd output then won't list the shared libraries and the detection will fail. Make sure nettle and others are really used.

Checklist

• Commits have Signed-off-by: with name/author being identical to the commit author

Reviewer's checklist:

• Any issues marked for closing are addressed
• There is a test suite reasonably covering new functionality or modifications
• Function naming, parameters, return values, types, etc., are consistent and according to CONTRIBUTION.md
• This feature/change has adequate documentation added
• No obvious mistakes in the code