fix flann_cpp.lib creaton on MSVC

src/cpp/CMakeLists.txt

@@ -42,6 +42,8 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_COMPILER_IS_GNUCC)
     endif()
 else()
     add_library(flann_cpp SHARED ${CPP_SOURCES})
+    # export lz4 headers, so that MSVC to creates flann_cpp.lib
+    set_target_properties(flann_cpp PROPERTIES WINDOWS_EXPORT_ALL_SYMBOLS YES)
     if (BUILD_CUDA_LIB)
 		cuda_add_library(flann_cuda SHARED ${CPP_SOURCES})
         set_property(TARGET flann_cpp PROPERTY COMPILE_DEFINITIONS FLANN_USE_CUDA)