fix install without static libzmq
fix install without static libzmq

If libzmq is only available as a shared library and not a static one
then cmake fails with:

-- CMake libzmq package not found, trying again with pkg-config (normal install of zeromq)
-- Found PkgConfig: /home/fabrice/buildroot/output/host/bin/pkg-config (found version "0.28")
CMake Error at CMakeLists.txt:20 (message):
  ZeroMQ was not found, neither as a CMake package nor via pkg-config

This is due to the fact that ZeroMQ_FOUND is not set to ON even if
ZEROMQ_LIBRARY is TRUE:

if(ZeroMQ_LIBRARY AND ZeroMQ_STATIC_LIBRARY)
    set(ZeroMQ_FOUND ON)
endif()

So change AND by OR as suggested in
https://github.com/zeromq/cppzmq/issues/266

Fix #266

Signed-off-by: Fabrice Fontaine <7d88633730b8b85c1516e612893df72eae9cd341@gmail.com>

zeromq/cppzmq,zeromq/cppzmq