Add semver pinning for Fabrikate to build.sh

As a: Developer

I want: build.sh to have a pinned major version of Fabrikate to download.

So that: Fabrikate developers can release new major versions which may break backwards compatibility (e.g. Adding Helm 3 support and dropping Helm 2)

Describe the solution you'd like: Add a major version pin to the build.sh script to determine which Fabrikate version to download.

e.g. if major = 0 then build.sh should download the latest Fabrikate binary matching v0.x.x.

Acceptance Criteria:

Describe alternatives you've considered:

Additional context: Depending on the timeliness this gets address, we are most likely going to have a release cadence in Fabrikate such that:

Does this require updates to documentation?:

microsoft / bedrock