cmake: Suppress compiler warnings from capnproto headers

Tweak target_link_libraries calls to correctly declare dependencies on
capnproto libraries as public, so capnproto include directories get correctly
added to downstream targets. Without this, compiler warnings can be triggered
from capnproto headers because they are not treated like external headers.

Fixes #138

Author: ryanofsky

CMakeLists.txt

@@ -95,10 +95,10 @@ target_include_directories(multiprocess PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   ${CAPNP_INCLUDE_DIRECTORY})
-target_link_libraries(multiprocess PRIVATE CapnProto::capnp)
-target_link_libraries(multiprocess PRIVATE CapnProto::capnp-rpc)
-target_link_libraries(multiprocess PRIVATE CapnProto::kj)
-target_link_libraries(multiprocess PRIVATE CapnProto::kj-async)
+target_link_libraries(multiprocess PUBLIC CapnProto::capnp)
+target_link_libraries(multiprocess PUBLIC CapnProto::capnp-rpc)
+target_link_libraries(multiprocess PUBLIC CapnProto::kj)
+target_link_libraries(multiprocess PUBLIC CapnProto::kj-async)
 set_target_properties(multiprocess PROPERTIES
     PUBLIC_HEADER "${MP_PUBLIC_HEADERS}")
 install(TARGETS multiprocess EXPORT LibTargets