cmake: examples: Build zmqproxy only for Linux
We only support ZMQ on general purpose OSes.  Build it for Linux for
now.
@@ -8,7 +8,9 @@ target_include_directories(csp_arch PRIVATE ${csp_inc})
target_link_libraries(csp_arch PRIVATE libcsp)
target_compile_definitions(csp_arch PRIVATE NDEBUG)
+if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
add_executable(zmqproxy EXCLUDE_FROM_ALL zmqproxy.c)
target_include_directories(zmqproxy PRIVATE ${csp_inc} ${LIBZMQ_INCLUDE_DIRS})
target_link_libraries(zmqproxy PRIVATE libcsp Threads::Threads ${LIBZMQ_LIBRARIES})
target_compile_definitions(zmqproxy PRIVATE NDEBUG)
+endif()
