testEncoding: use cmsys::ifstream

Tests/CMakeLib/testEncoding.cxx

-#include <fstream>
+#include <cmsys/FStream.hxx>
 #include <iostream>
 #include <string>
 
@@ -39,7 +39,7 @@ int main(int argc, char* argv[])
     setEncoding(consoleOut, CP_OEMCP);
   } // else AUTO
 #endif
-  std::ifstream file(argv[2]);
+  cmsys::ifstream file(argv[2]);
   if (!file.is_open()) {
     std::cout << "Failed to open file: " << argv[2] << std::endl;
     return 2;