build: make build fail if unresolved symbols found

build: make build fail if unresolved symbols found

gcc links shared libs also when there are still some unresolved
symbols, you have to specify it explicitly to make it fail in such
cases. I think a compiler should fail in such cases otherwise
someone will add some not intended dependencies or some existing
dependencies are not getting declared.

This patch makes gcc fail in such cases. I have only activated this for
libs build in a Linux build and explicitly deactivates it for windows
(does this even work at all?) This should be build tested with Android
also.

This was build tested for Linux and Android.

This patch depends on some other patches I send which are fixing the
problems I found with this change.

Change-Id: I9ab79896ca2e86e9226cd9b39060a0763ef89694
Signed-off-by: Hauke Mehrtens <hauke.mehrtens@lantiq.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1802
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Reviewed-by: Hun-je Yeon <hunje.yeon@samsung.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>