GCC 10.0.1 compile error

[rvianello]

Configuration:

• RDKit Version: 2020.03.1, and also the current tip of the master branch
• Operating system: linux (Fedora 32)
• Python version (if relevant): not relevant
• Are you using conda?
• If you are using conda, which channel did you install the rdkit from?
• If you are not using conda: how did you install the RDKit?

Description:

The new Fedora 32 release upgrades the default gcc compilers to version 10.0.1. A build of the RDKit C++ libraries fails with the following error:

/Code/GraphMol/catch_sgroups.cpp:210:6: error: could not convert ‘{{{{{{1.0e+0, 3.0e+0, 0.0}}, {{5.0e+0, 7.0e+0, 0.0}}, {{0.0, 0.0, 0.0}}}}, {{{{2.0e+0, 4.0e+0, 0.0}}, {{6.0e+0, 8.0e+0, 0.0}}, {{0.0, 0.0, 0.0}}}}}}’ from ‘<brace-enclosed initializer list>’ to ‘std::vector<std::array<std::array<double, 3>, 3> >’
  210 |     }};
      |      ^
      |      |
      |      <brace-enclosed initializer list>

I'm not sure if it's the proper fix, but, replacing the outermost double braces with single ones, apparently fixes the compile-time error. A similar fix also applies in two locations inside /Code/GraphMol/testSGroup.cpp.