[BOLT] Ignore empty funcs in relocation mode

Summary:
Make BOLT ignore empty functions (those containing no instructions,
despite having some space allocated to it filled with zeroes).

(cherry picked from FBD15981683)

bolt/src/BinaryFunction.cpp

@@ -1329,6 +1329,12 @@ void BinaryFunction::postProcessEntryPoints() {
         continue;
       }
 
+      // If we are at Offset 0 and there is no instruction associated with it,
+      // this means this is an empty function. Just ignore.
+      if (Offset == 0) {
+        continue;
+      }
+
       errs() << "BOLT-WARNING: reference in the middle of instruction "
                 "detected in function " << *this
              << " at offset 0x" << Twine::utohexstr(Offset) << '\n';