DO NOT MERGE Rebuild with gcc 10 for pybind11 compatiblity when building GR OOT modules

[ryanvolz]

Checklist

• Used a personal fork of the feedstock to propose changes
• Bumped the build number (if the version is unchanged)
• Re-rendered with the latest conda-smithy (Use the phrase @conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[ryanvolz]

Actually, to avoid any issues with installing pybind-incompatible gnuradio and OOT packages, updating to GCC 10 should wait until a 3.x.x version update. That's annoying if we have any other package updates or OOT updates in the meantime, but I don't want to be fielding lots of pybind11 incompatibility bug reports.

[ryanvolz]

With the switch from GCC 9 to GCC 10, the issue is that the internal pybind11 identifier changes from

__pybind11_internals_v4_gcc_libstdcpp_cxxabi1013__

to

__pybind11_internals_v4_gcc_libstdcpp_cxxabi1014__

According to pybind/pybind11#2602, we could override this by defining

#define PYBIND11_BUILD_ABI ""

when building gnuradio and any OOTs.