src/Makefile: Only specify -shared at link time

Since -shared only takes effect when linking, only specify it when linking.
This patch fixes the following clang warning:

clang-10.0: warning: argument unused during compilation: '-shared' [-Wunused-command-line-argument]

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
1 file changed