Builder - Define go version in manifest

[djaglowski]

Is your feature request related to a problem? Please describe.

The builder currently hardcodes the version of go into the code generated by the builder. If we move the go version into the manifest file itself, this would potentially allow someone to generate exactly the same binary, given only the manifest file.

Describe the solution you'd like

Move the go version into the manifest file. Update the builder's go.mod template to write the go version.