stunt ld: Drop (LTO) -plugin and -plugin-opt from ld command

With (at least) GCC 4.9 on Debian jessie the GCC spec files have changed
to always use -plugin / -plugin-opt and load the LTO plugin, even if
-flto is not specified to GCC.

This breaks stunt ld which does not understand these options. Dropping
them from the linker command appears to do no harm.
Merge pull request #9 from mato/wip-gcc49-lto

Fix non-working stunt ld with GCC 4.9 on Debian