Revert r247216: "Fix Clang-tidy misc-use-override warnings, other minor fixes"

This caused build breakges, e.g.
http://lab.llvm.org:8011/builders/clang-x86_64-ubuntu-gdb-75/builds/24926

llvm-svn: 247226
diff --git a/llvm/lib/CodeGen/MIRPrintingPass.cpp b/llvm/lib/CodeGen/MIRPrintingPass.cpp
index 8e7566a..13d61e6 100644
--- a/llvm/lib/CodeGen/MIRPrintingPass.cpp
+++ b/llvm/lib/CodeGen/MIRPrintingPass.cpp
@@ -40,7 +40,7 @@
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 
-  bool runOnMachineFunction(MachineFunction &MF) override {
+  virtual bool runOnMachineFunction(MachineFunction &MF) override {
     std::string Str;
     raw_string_ostream StrOS(Str);
     printMIR(StrOS, MF);
@@ -48,7 +48,7 @@
     return false;
   }
 
-  bool doFinalization(Module &M) override {
+  virtual bool doFinalization(Module &M) override {
     printMIR(OS, M);
     OS << MachineFunctions;
     return false;