Provide anchor for compiler extensions

Author: Serge Guelton

llvm/lib/Extensions/Extensions.cpp

@@ -0,0 +1,15 @@
+#include "llvm/Passes/PassPlugin.h"
+#define HANDLE_EXTENSION(Ext)                                                  \
+		llvm::PassPluginLibraryInfo get##Ext##PluginInfo();
+#include "llvm/Support/Extension.def"
+
+
+namespace llvm {
+	namespace details {
+		void extensions_anchor() {
+#define HANDLE_EXTENSION(Ext)                                                  \
+			static auto Ext = get##Ext##PluginInfo();
+#include "llvm/Support/Extension.def"
+		}
+	}
+}