Add WINDOWS_EXPORT_ALL_SYMBOLS property to flann_cpp only.

ports/flann/CONTROL

@@ -1,3 +1,3 @@
 Source: flann
-Version: 1.9.1
+Version: 1.9.1-1
 Description: Fast Library for Approximate Nearest Neighbors

ports/flann/export-all-symbols-of-flann-cpp.patch

@@ -0,0 +1,12 @@
+diff --git a/src/cpp/CMakeLists.txt b/src/cpp/CMakeLists.txt
+index 49c53f0..b9cf76b 100644
+--- a/src/cpp/CMakeLists.txt
++++ b/src/cpp/CMakeLists.txt
+@@ -52,6 +52,7 @@ set_target_properties(flann_cpp PROPERTIES
+    VERSION ${FLANN_VERSION}
+    SOVERSION ${FLANN_SOVERSION}
+    DEFINE_SYMBOL FLANN_EXPORTS
++   WINDOWS_EXPORT_ALL_SYMBOLS ON
+ )
+ 
+ if (BUILD_CUDA_LIB)

ports/flann/portfile.cmake

@@ -19,10 +19,19 @@ vcpkg_download_distfile(ARCHIVE
 )
 vcpkg_extract_source_archive(${ARCHIVE})
 
+vcpkg_apply_patches(
+    SOURCE_PATH ${SOURCE_PATH}
+    PATCHES "${CMAKE_CURRENT_LIST_DIR}/export-all-symbols-of-flann-cpp.patch"
+)
+
 vcpkg_configure_cmake(
     SOURCE_PATH ${SOURCE_PATH}
     PREFER_NINJA # Disable this option if project cannot be built with Ninja
-    OPTIONS -DCMAKE_WINDOWS_EXPORT_ALL_SYMBOLS=ON -DBUILD_EXAMPLES=OFF -DBUILD_DOC=OFF -DBUILD_PYTHON_BINDINGS=OFF -DBUILD_MATLAB_BINDINGS=OFF
+    OPTIONS
+        -DBUILD_EXAMPLES=OFF
+        -DBUILD_DOC=OFF
+        -DBUILD_PYTHON_BINDINGS=OFF
+        -DBUILD_MATLAB_BINDINGS=OFF
 )
 
 vcpkg_install_cmake()