[clangd] Update clangDaemonTweaks to set symbol visibility macros correctly

This will fix linker duplicate symbols errors from clangDaemonTweaks exporting
clang symbols instead of importing them for windows shared library builds using
explicit symbol visibly.

This is part of the work to enable LLVM_BUILD_LLVM_DYLIB and LLVM/Clang
plugins on window.

Author: fsfod

clang-tools-extra/clangd/refactor/tweaks/CMakeLists.txt

@@ -11,7 +11,7 @@ set(LLVM_LINK_COMPONENTS
 # To enable these tweaks in executables or shared libraries, add
 # $<TARGET_OBJECTS:obj.clangDaemonTweaks> to a list of sources, see
 # clangd/tool/CMakeLists.txt for an example.
-add_clang_library(clangDaemonTweaks OBJECT
+add_clang_library(clangDaemonTweaks CLANG_IMPORT OBJECT
   AddUsing.cpp
   AnnotateHighlightings.cpp
   DumpAST.cpp

clang/cmake/modules/AddClang.cmake

@@ -47,7 +47,7 @@ endmacro()
 
 macro(add_clang_library name)
   cmake_parse_arguments(ARG
-    "SHARED;STATIC;INSTALL_WITH_TOOLCHAIN"
+    "SHARED;STATIC;INSTALL_WITH_TOOLCHAIN;CLANG_IMPORT"
     ""
     "ADDITIONAL_HEADERS"
     ${ARGN})
@@ -114,7 +114,7 @@ macro(add_clang_library name)
     if(TARGET "obj.${name}")
       target_compile_definitions("obj.${name}" PUBLIC CLANG_BUILD_STATIC)
     endif()
-  elseif(NOT ARG_SHARED AND NOT ARG_STATIC)
+  elseif(NOT ARG_SHARED AND NOT ARG_STATIC AND NOT ARG_CLANG_IMPORT)
     # Clang component libraries linked in to clang-cpp are declared without SHARED or STATIC
     target_compile_definitions("obj.${name}" PUBLIC CLANG_EXPORTS)
   endif()