#ifdef PLATFORM_WIN32
   #include <windows.h>
#endif

...

#ifdef PLATFORM_WIN32
    strcpy( a, commandline);
    wchar aa[1000];
    wcscpy(aa, commandline.ToWString());

    STARTUPINFOW si;  //STARTUPINFO si; //for char
    PROCESS_INFORMATION pi;
    ZeroMemory( &si, sizeof(si) );
    si.cb = sizeof(si);
    ZeroMemory( &pi, sizeof(pi) );

    CreateProcessW( NULL,   // No module name (use command line)
        aa,         // Command line for wchar
        NULL,           // Process handle not inheritable
        NULL,           // Thread handle not inheritable
        FALSE,          // Set handle inheritance to FALSE
        CREATE_NO_WINDOW, //0,              // No creation flags
        NULL,           // Use parent's environment block
        NULL,           // Use parent's starting directory 
        &si,            // Pointer to STARTUPINFO structure
        &pi );           // Pointer to PROCESS_INFORMATION structure

    // Wait until child process exits.
    WaitForSingleObject( pi.hProcess, INFINITE );

    // Close process and thread handles. 
    CloseHandle( pi.hProcess );
    CloseHandle( pi.hThread );
#else 
...