Fails to build with non c++11 compilers

[tenomoto]

eigen fails to build with gcc5. On FreeBSD 11-RELEASE, the problem can be fixed by adding -std=c++11 to the compile options or switch the compiler to system clang in lib/Makefile. It would be better not to hard code the compiler. I suggest using CXX and CXXFLAGS. Wtih clang -lstdc++ should be replaced with -lc++ in _oasis.

[ryanrhymes]

@tenomoto Thanks for reporting this, really appreciate it. I agree with your suggestion. Would you like to create a PR to fix this issue on FreeBSD?

[mseri]

Now that we are using dune this would be quite easy to fix: we could add a configurator step creating the right flags, or using ocaml syntax in the dune file

[mseri]

Is this still a problem?