Update macOS Build Instructions

[dechilders]

Added build instructions for gr-osmosdr since it is no longer available from Homebrew.
Added pybind11 as a dependency for building gr-osmosdr.

[robotastic]

Ah Good catch! Thanks for making the update

[e850205]

I had to use a different path for openssl to build on Mac - /opt/homebrew/Cellar/openssl@3/3.0.3

So the command for me was:
cmake ../source -DOPENSSL_ROOT_DIR=/opt/homebrew/Cellar/openssl@3/3.0.3

[e850205]

Can't make on Mac right now anyways

"In file included from /Users//trunk-recorder/source/trunk-recorder/systems/system_impl.cc:1:
/Users//trunk-recorder/source/trunk-recorder/systems/system.h:40:59: error: unknown type name 'ß'"

[taclane]

I had to use a different path for openssl to build on Mac - /opt/homebrew/Cellar/openssl@3/3.0.3

So the command for me was: cmake ../source -DOPENSSL_ROOT_DIR=/opt/homebrew/Cellar/openssl@3/3.0.3

Homebrew installs in /opt/homebrew on apple silicon, and /usr/local on intel.
To keep both bases covered, the cmake command using homebrew could simply be:

cmake .. -DOPENSSL_ROOT_DIR=$(brew --prefix openssl)