[ELF2] In/out parameter of writeGlobalSymbols() is changed to in parameter.

There is no outer code which requires the changed value.

llvm-svn: 250688
diff --git a/lld/ELF/OutputSections.h b/lld/ELF/OutputSections.h
index 0892ce8..d8fc041 100644
--- a/lld/ELF/OutputSections.h
+++ b/lld/ELF/OutputSections.h
@@ -148,7 +148,7 @@
 
 private:
   void writeLocalSymbols(uint8_t *&Buf);
-  void writeGlobalSymbols(uint8_t *&Buf);
+  void writeGlobalSymbols(uint8_t *Buf);
 
   SymbolTable<ELFT> &Table;
   StringTableSection<ELFT> &StrTabSec;