run_osx_build.sh: include 'make_build_number' and cross-compile check in 'Configuring conda' group
run_osx_build.sh: include 'make_build_number' and cross-compile check in 'Configuring conda' group

This follows what is done on the Linux side in 'build_steps.sh'.

conda-forge/conda-smithy,conda-forge/conda-smithy