GitHub Actions needs to be updated for 1.12.2 build

[fr1kin]

Currently actions is not configured to build 1.12.2 builds properly. Easiest way to deal with this is to just copy what I have done on the 1.16 branch over to the 1.12.2 (master) branch but include the additional necessary build processes (setupDecompWorkspace)

[fr1kin]

I am not able to build the 1.12 branch anymore. Not sure what happened but a clean install will always fail.