Add "used" attribute to XML data symbol when creating compressed config

The __attribute__((used)) tells the compiler not to make the symbol
local when optimizing. This happens when LTO is used when building a
VESC package.

utility.cpp

@@ -1427,7 +1427,7 @@ bool Utility::createCompressedConfigC(ConfigParams *params, QString configName,
 
     outSource << "// This file is autogenerated by VESC Tool\n\n";
     outSource << "#include \"" << headerInfo.fileName() << "\"\n\n";
-    outSource << "uint8_t data_" << configNameStr << "[" << compressed.size() << "] = {\n\t";
+    outSource << "__attribute__((used)) uint8_t data_" << configNameStr << "[" << compressed.size() << "] = {\n\t";
 
     int posCnt = 0;
     for (auto b: compressed) {