windows: fix DLL build

src/libespeak-ng/CMakeLists.txt

 endif()
 target_link_libraries(espeak-ng PUBLIC espeak-include)
 
+if ((MINGW OR WIN32 OR MSVC) AND BUILD_SHARED_LIBS)
+  set_target_properties(espeak-ng PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY ..
+  )
+endif()
+
 install(TARGETS espeak-ng LIBRARY)

tests/CMakeLists.txt

   target_link_libraries(test_${_test_name} PRIVATE
     $<TARGET_PROPERTY:espeak-ng,LINK_LIBRARIES>
   )
+  target_compile_definitions(test_${_test_name} PRIVATE LIBESPEAK_NG_EXPORT=1)
   target_include_directories(
     test_${_test_name} PRIVATE
     $<TARGET_PROPERTY:espeak-ng,SOURCE_DIR>