[BOLT] Fix profile for multi-entry functions

Summary:
When we read profile for functions, we initialize counts for entry
blocks first, and then populate counts for all blocks based
on incoming edges.

During the second phase we ignore the entry blocks because we expect
them to be already initialized. For the primary entry at offset 0 it's
the correct thing to do, since we treat all incoming branches as calls
or tail calls. However, for secondary entries we only consider external
edges to be from calls and don't increase entry count if an edge
originates from inside the function. Thus we need to update the
secondary entry basic block counts with internal edges too.

(cherry picked from FBD6836817)

bolt/BinaryFunctionProfile.cpp

@@ -366,8 +366,10 @@ void BinaryFunction::postProcessProfile() {
   for (auto *BB : BasicBlocks) {
     auto SuccBIIter = BB->branch_info_begin();
     for (auto Succ : BB->successors()) {
-      if (!Succ->isEntryPoint() &&
-          SuccBIIter->Count != BinaryBasicBlock::COUNT_NO_PROFILE)
+      // All incoming edges to the primary entry have been accounted for, thus
+      // we skip the update here.
+      if (SuccBIIter->Count != BinaryBasicBlock::COUNT_NO_PROFILE &&
+          Succ != BasicBlocks.front())
         Succ->setExecutionCount(Succ->getExecutionCount() + SuccBIIter->Count);
       ++SuccBIIter;
     }