base64 application on Mac is different to base64 application on Linux

[kevaundray]

Problem

In the barretenberg binary, we call base64 and pipe that output to gunzip. The base64 call assumes that Mac and Linux both have the same command line options and implementations, which is not the case.

Solution

Conditionally compile the statement which uses the base64 application

[kevaundray]

Note: we don't test on mac which is why this was not caught. It was not caught earlier in Noir because we were using nix which installs a base64 package in the sandbox which uses the "linux" version of base64 regardless of OS

[kevaundray]

Another way to do this which avoids the conditional compilation but it creates an intermediate file that you need to clean up is:

base64 -d < file > temp_output && gunzip < temp_output

As noted, you need to clean up temp_output so its not that desirable -- given that removing base64 encoding has been floated, I think we can live with conditional compilation for now