[libclang] Revert removal of tidy plugin support from libclang introduced in r347496

Differential Revision: https://reviews.llvm.org/D55415

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@348764 91177308-0d34-0410-b5e6-96231b3b80d8

tools/libclang/CIndex.cpp

@@ -8938,3 +8938,16 @@ cxindex::Logger::~Logger() {
     OS << "--------------------------------------------------\n";
   }
 }
+
+#ifdef CLANG_TOOL_EXTRA_BUILD
+// This anchor is used to force the linker to link the clang-tidy plugin.
+extern volatile int ClangTidyPluginAnchorSource;
+static int LLVM_ATTRIBUTE_UNUSED ClangTidyPluginAnchorDestination =
+    ClangTidyPluginAnchorSource;
+
+// This anchor is used to force the linker to link the clang-include-fixer
+// plugin.
+extern volatile int ClangIncludeFixerPluginAnchorSource;
+static int LLVM_ATTRIBUTE_UNUSED ClangIncludeFixerPluginAnchorDestination =
+    ClangIncludeFixerPluginAnchorSource;
+#endif

tools/libclang/CMakeLists.txt

@@ -47,6 +47,15 @@ if (CLANG_ENABLE_ARCMT)
   list(APPEND LIBS clangARCMigrate)
 endif ()
 
+if (TARGET clangTidyPlugin)
+  add_definitions(-DCLANG_TOOL_EXTRA_BUILD)
+  list(APPEND LIBS clangTidyPlugin)
+  list(APPEND LIBS clangIncludeFixerPlugin)
+  if(LLVM_ENABLE_MODULES)
+    list(APPEND LLVM_COMPILE_FLAGS "-fmodules-ignore-macro=CLANG_TOOL_EXTRA_BUILD")
+  endif()
+endif ()
+
 find_library(DL_LIBRARY_PATH dl)
 if (DL_LIBRARY_PATH)
   list(APPEND LIBS dl)