targets/dri: move linker flags out of configure into Automake.inc

targets/dri: move linker flags out of configure into Automake.inc

Previous assumption was that the same set of flags can be reused
for both classic and gallium drivers. With megadriver work done
the classic drivers ended up using their own (single) instance of
the flags.

Move these into Automake.inc and rename to indicate that those
are gallium specific. Additionally silence an automake/autoconf
warning "XXX is not a standard libtool library name", due to
the parsing issues of the module tag.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>