[EraVM] Use full keccak256 hash value for linker symbols

EF compiler uses only 18 bytes of the keccak256 hash value
when hashing linker symbols. Probably it's done to limit
size of unlinked contracts by increasing collision probability.
But this doesn't seem to make a big sense, so lets use full hash
values. Anyway, this doesn't affect size of executable bytecode.

Author: PavelKopyl

llvm/lib/Target/EraVM/MCTargetDesc/EraVMMCTargetDesc.cpp

@@ -128,12 +128,12 @@ EraVM::analyzeEncodedOpcode(unsigned EncodedOpcode, EncodedOperandMode &SrcMode,
 }
 
 // Returs the string of the following format:
-//   '__$KECCAK256(SymName.substr(0, 34))$__'
+//   '__$KECCAK256(SymName)$__'
 std::string EraVM::getLinkerSymbolHash(StringRef SymName) {
   std::array<uint8_t, 32> Hash = KECCAK::KECCAK_256(SymName);
   SmallString<72> HexHash;
   toHex(Hash, /*LowerCase*/ true, HexHash);
-  return (Twine("__$") + HexHash.substr(0, 34) + "$__").str();
+  return (Twine("__$") + HexHash + "$__").str();
 }
 
 // Returns concatenation of the Name with the SubIdx.