mk: use whole-archive option to keep unused symbols

mk: use whole-archive option to keep unused symbols

To fully support dpdk extensions (loading of .so), all symbols provided
by dpdk libraries must be available in the binaries: before this patch,
unused functions/variables from dpdk static libraries could be stripped
by the linker because they are not used. These symbols can be used by a
dpdk extension that is loaded at runtime with the -d option.

Adding --whole-archive when generating a binary solves this issue.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Thomas Monjalon <thomas.monjalon@6wind.com>