games/blackshadeselite: fix build on GCC architectures

OpenAL now needs C++11 compiler:
/usr/local/lib/libopenal.so: undefined reference to `std::runtime_error::runtime_error(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)@GLIBCXX_3.4.21'