[NFC][Debugify] Format the CheckModuleDebugify output

[djtodoro]

Summary

This fixes the output of the check-debugify option.
Without the patch an example of running the option:

$ opt -check-debugify test.ll -S -o testDebugify.ll
CheckModuleDebugifySkipping module without debugify metadata

After the patch:

$ opt -check-debugify test.ll -S -o testDebugify.ll
CheckModuleDebugify: Skipping module without debugify metadata

[djtodoro]

• posting the right patch

llvm/lib/Transforms/Utils/Debugify.cpp

 
 bool checkDebugifyMetadata(Module &M,
                            iterator_range<Module::iterator> Functions,
                            StringRef NameOfWrappedPass, StringRef Banner,
                            bool Strip, DebugifyStatsMap *StatsMap) {
   // Skip modules without debugify metadata.
   NamedMDNode *NMD = M.getNamedMetadata("llvm.debugify");
   if (!NMD) {
-    dbg() << Banner << "Skipping module without debugify metadata\n";
+    dbg() << Banner << ": Skipping module without debugify metadata\n";
     return false;
   }
 
   auto getDebugifyOperand = [&](unsigned Idx) -> unsigned {
     return mdconst::extract<ConstantInt>(NMD->getOperand(Idx)->getOperand(0))
         ->getZExtValue();
   };
   assert(NMD->getNumOperands() == 2 &&