Fix broken OSX build due to azidentity caching enablement

[sanelson]

Enabling caching using azidentity had the side effect of breaking the current cross-platform build for OSX. The automated build broke with the following error:

# github.com/Azure/azure-sdk-for-go/sdk/azidentity/cache
Error: ../../../go/pkg/mod/github.com/!azure/azure-sdk-for-go/sdk/azidentity/cache@v0.3.1/darwin.go:18:19: undefined: accessor.New
Error: ../../../go/pkg/mod/github.com/!azure/azure-sdk-for-go/sdk/azidentity/cache@v0.3.1/darwin.go:18:38: undefined: accessor.WithAccount
An error has occurred! Aborting the script execution...
Error: Process completed with exit code 1.

This is referenced in a issue here and also in the azidentity docs.

Should be fixed by adding CGO_ENABLED=1 to the environment for the OSX builds. As of now it should not be required for Linux & Windows builds.