Baremetal: Fix compile for older compiler and Qt

Change-Id: I7756fcb575c5e508933d3bffb2926b90b1e70748
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/baremetal/sdcctoolchain.cpp

@@ -69,7 +69,7 @@ static QString compilerTargetFlag(const Abi &abi)
 {
     switch (abi.architecture()) {
     case Abi::Architecture::Mcs51Architecture:
-        return "-mmcs51";
+        return QString("-mmcs51");
     default:
         return {};
     }