mk: fix objects and libraries order when linking

mk: fix objects and libraries order when linking

The initial problem has been seen while building mlx4 pmd as a shared
library on Ubuntu 14.04 (gcc 4.8.4-2ubuntu1~14.04).

Resulting .so will lack the DT_NEEDED entry for libibverbs:

marchand@ubuntu1404:~/dpdk$ ldd ./build/lib/librte_pmd_mlx4.so
	linux-vdso.so.1 =>  (0x00007fff87ebb000)
	libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f2ced21a000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f2ced821000)

And trying to load it in testpmd triggers this error:

[...]
EAL: librte_pmd_mlx4.so: undefined symbol: ibv_query_port
[...]

After some strace, the problem comes from the --as-needed option passed to the
linker.

It is safer to specify libraries we depend on after the objects we are linking
into a shared library, especially when the linker is invoked with options like
--as-needed.

Fixes: bef06a8a0655 ("mk: set library dependencies in shared object file")
Signed-off-by: David Marchand <david.marchand@6wind.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>