zeromq: patch configure.ac to check for ldaddr on when checking libunwind

configure.ac can fail the build when there's no dynamic library support,
since it cannot find dladdr which is needed only when we have libunwind.
Therefore, configure.ac was patched to check for dladdr only in the libunwind
check section. As a consequence of the patch, ZEROMQ_AUTORECONF was set.

The patch was applied to the zeromq master branch, see:
https://github.com/zeromq/libzmq/commit/c971445025535b9f989ab0b78f5ddd1c026f1878

Fixes:
http://autobuild.buildroot.net/results/2b1aaf7e35651f04a9e9d0269e49c1b0bd87ae29/



Signed-off-by: Asaf Kahlon <asafka7@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>