cmCoreTryCompile: Remove variable assignment.

The variable is not a reference, and we return in the same scope
after assigning, so it has no effect.

Source/cmCoreTryCompile.cxx

@@ -685,8 +685,7 @@ void cmCoreTryCompile::FindOutputFile(const std::string& targetName)
     command += tmpOutputFile;
     if(cmSystemTools::FileExists(command.c_str()))
       {
-      tmpOutputFile = cmSystemTools::CollapseFullPath(command);
-      this->OutputFile = tmpOutputFile;
+      this->OutputFile = cmSystemTools::CollapseFullPath(command);
       return;
       }
     }