build: integrate prepare source from composer

[lzap]

I noticed this automated PR failed:

#1475

This is a chance to integrate changes from composer which uses a new Go feature "toolbox", hopefully it will prevent from automated failures.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

[lzap]

Hey @croissanne and @ezr-ondrej this needs an attention - other PRs are failing because of a version requirement, I believe it is great time to fix prepare sources for once.

There is a tread on #osbuild channel about this, this was merged into composer, then reverted by @achilleas-k and now the final version is heading in: osbuild/osbuild-composer#4600 also being integrated elsewhere: osbuild/weldr-client#155

[lzap]

The TOOLS_PATH will disappear once we upgrade to 1.24 which features the all new Go tool pinning feature. In short, external tools will be added to go.mod now ensuring we all are on the same version. Until then, this is I believe a good workaround for the time being.