8247818: GCC 10 warning stringop-overflow with symbol code

Backport-of: ed31b66

src/hotspot/share/oops/symbol.cpp

@@ -52,9 +52,7 @@ uint32_t Symbol::pack_length_and_refcount(int length, int refcount) {
 Symbol::Symbol(const u1* name, int length, int refcount) {
   _length_and_refcount =  pack_length_and_refcount(length, refcount);
   _identity_hash = (short)os::random();
-  for (int i = 0; i < length; i++) {
-    byte_at_put(i, name[i]);
-  }
+  memcpy(_body, name, length);
 }
 
 void* Symbol::operator new(size_t sz, int len) throw() {

src/hotspot/share/oops/symbol.hpp

@@ -126,11 +126,6 @@ class Symbol : public MetaspaceObj {
     return (int)heap_word_size(byte_size(length));
   }
 
-  void byte_at_put(int index, u1 value) {
-    assert(index >=0 && index < length(), "symbol index overflow");
-    _body[index] = value;
-  }
-
   Symbol(const u1* name, int length, int refcount);
   void* operator new(size_t size, int len) throw();
   void* operator new(size_t size, int len, Arena* arena) throw();