Fix defining the macro in cmake to control c++ symbol visibility for libclang on windows

Author: fsfod

clang/tools/libclang/CMakeLists.txt

@@ -166,7 +166,11 @@ if(ENABLE_SHARED)
     set_target_properties(libclang
       PROPERTIES
       VERSION ${LIBCLANG_LIBRARY_VERSION}
-      DEFINE_SYMBOL _CINDEX_LIB_  DEFINE_SYMBOL CLANG_EXPORTS)
+      DEFINE_SYMBOL _CINDEX_LIB_)
+      # Avoid declaring clang c++ symbols that are statically linked into libclang as dllimport'ed.
+      # If llvm/libclang-cpp dll is also being built for windows clang c++ symbols will still be
+      # implicitly be exported from libclang.
+      target_compile_definitions(libclang PRIVATE CLANG_BUILD_STATIC)
   elseif(APPLE)
     set(LIBCLANG_LINK_FLAGS " -Wl,-compatibility_version -Wl,1")
     set(LIBCLANG_LINK_FLAGS "${LIBCLANG_LINK_FLAGS} -Wl,-current_version -Wl,${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}.${LLVM_VERSION_PATCH}")