Default to -fcf-protection=branch
May need to be tweaked if ldc grows !amd64 packages...

Index: driver/cl_options_instrumentation.cpp
--- driver/cl_options_instrumentation.cpp.orig
+++ driver/cl_options_instrumentation.cpp
@@ -95,7 +95,7 @@ cl::opt<CFProtectionType> fCFProtection(
                clEnumValN(CFProtectionType::Full, "",
                           "") // default to "full" if no argument specified
                ),
-    cl::init(CFProtectionType::None));
+    cl::init(CFProtectionType::Branch));
 
 void initializeInstrumentationOptionsFromCmdline(const llvm::Triple &triple) {
   if (ASTPGOInstrGenFile.getNumOccurrences() > 0) {