Merge multiple Project build jobs

[abhiTronix]

This proposal is to merge and shrink project's different GCC jobs (based on GCC versions, RpiOS types etc.) for each Pi type, into a much simpler/compact form using GitHub Actions jobs.<job_id>.strategy.matrix where, you can easily define a matrix of different job configurations. A matrix allows you to create multiple jobs by performing variable substitution in a single job definition.