Create SampleProfileLoader pass in llvm instead of clang

[danielcdh]

Summary

We used to create SampleProfileLoader pass in clang. This makes LTO/ThinLTO unable to add this pass in the linker plugin. This patch moves the SampleProfileLoader pass creation from
clang to llvm pass manager builder.

[dnovillo]

LGTM

[danielcdh]

was reverted due to bot breaking

lib/CodeGen/BackendUtil.cpp

if (CodeGenOpts.hasProfileIRInstr()) {
     if (!CodeGenOpts.InstrProfileOutput.empty())
       PMBuilder.PGOInstrGen = CodeGenOpts.InstrProfileOutput;
     else
       PMBuilder.PGOInstrGen = "default_%m.profraw";
   }
   if (CodeGenOpts.hasProfileIRUse())
     PMBuilder.PGOInstrUse = CodeGenOpts.ProfileInstrumentUsePath;
 
-  if (!CodeGenOpts.SampleProfileFile.empty()) {
-    MPM.add(createPruneEHPass());
-    MPM.add(createSampleProfileLoaderPass(CodeGenOpts.SampleProfileFile));
-  }
+  if (!CodeGenOpts.SampleProfileFile.empty())
+    PMBuilder.PGOSampleUse = CodeGenOpts.SampleProfileFile;
 
   PMBuilder.populateFunctionPassManager(FPM);
   PMBuilder.populateModulePassManager(MPM);
 }
 
 void EmitAssemblyHelper::setCommandLineOpts() {
   SmallVector<const char *, 16> BackendArgs;
   BackendArgs.push_back("clang"); // Fake program name.