Fix --print-icf-sections output.

Previously, multiple chunks of --print-icf-sections messages were interleaved
and didn't make sense. This is because forEachClass is multi-threaded.

llvm-svn: 324683

lld/ELF/ICF.cpp

@@ -439,7 +439,7 @@ template <class ELFT> void ICF<ELFT>::run() {
   };
 
   // Merge sections by the equivalence class.
-  forEachClass([&](size_t Begin, size_t End) {
+  forEachClassRange(0, Sections.size(), [&](size_t Begin, size_t End) {
     if (End - Begin == 1)
       return;