enable visibility control for building on Win32

we still have no functionality on Windows, but at least it compiles

tracetools/CMakeLists.txt

@@ -48,13 +48,18 @@ if(TRACING_ENABLED)
   target_compile_definitions(${PROJECT_NAME} PUBLIC TRACETOOLS_LTTNG_ENABLED)
   target_link_libraries(${PROJECT_NAME} ${LTTNG_LIBRARIES} -ldl)
 endif()
+if(WIN32)
+    # Causes the visibility macros to use dllexport rather than dllimport
+    # which is appropriate when building the dll but not consuming it.
+    target_compile_definitions(${PROJECT_NAME}
+      PRIVATE "TRACETOOLS_BUILDING_DLL")
+endif()
 
 ament_export_interfaces(${PROJECT_NAME}_export HAS_LIBRARY_TARGET)
 
 # Status checking tool
 add_executable(status
   src/status.c
-  src/tracetools.c
   src/utils.cpp
 )
 target_link_libraries(status