[llvm-profgen] Fix warnings when building without asserts [NFC]

Building without asserts we got:
 ../tools/llvm-profgen/ProfiledBinary.cpp:627:14: error: unused variable 'Err' [-Werror,-Wunused-variable]
   627 |         bool Err = MIA->evaluateBranch(Inst, Address, Size, Target);
       |              ^~~
 ../tools/llvm-profgen/ProfiledBinary.cpp:1172:14: error: unused variable 'TopProbe' [-Werror,-Wunused-variable]
  1172 |         auto TopProbe = TopLevelProbes.begin();
       |              ^~~~~~~~
 2 errors generated.

Add [[maybe_unused]] to the variables just used in asserts.

Author: mikaelholmen

llvm/tools/llvm-profgen/ProfiledBinary.cpp

@@ -624,7 +624,8 @@ bool ProfiledBinary::dissassembleSymbol(std::size_t SI, ArrayRef<uint8_t> Bytes,
       // Record potential call targets for tail frame inference later-on.
       if (InferMissingFrames && FRange) {
         uint64_t Target = 0;
-        bool Err = MIA->evaluateBranch(Inst, Address, Size, Target);
+        [[maybe_unused]] bool Err =
+            MIA->evaluateBranch(Inst, Address, Size, Target);
         if (MCDesc.isCall()) {
           // Indirect call targets are unknown at this point. Recording the
           // unknown target (zero) for further LBR-based refinement.
@@ -1169,7 +1170,7 @@ void ProfiledBinary::loadSymbolsFromPseudoProbe() {
               InlineTreeNode->Parent);
 
         auto TopLevelProbes = InlineTreeNode->getProbes();
-        auto TopProbe = TopLevelProbes.begin();
+        [[maybe_unused]] auto TopProbe = TopLevelProbes.begin();
         assert(TopProbe != TopLevelProbes.end() &&
                TopProbe->getAddress() >= StartAddr &&
                TopProbe->getAddress() < EndAddr &&