Make beyla-genfiles self-contained

[rafaelroquetto]

This PR embeds the beyla-genfile binary in the generator image, to allow downstream software vendoring Beyla to run this tool without having to explicitly fetch its source code and provide it to the image (that only works when building beyla itself, as tools are not distributed as vendored modules).

This relates to grafana/alloy#2734

[rafaelroquetto]

The previous approach of calling go run will not work on downstream projects pulling Beyla

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 18 lines in your changes missing coverage. Please review.

Project coverage is 66.98%. Comparing base (49c45f6) to head (62c78aa).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/beyla-genfiles/beyla_genfiles.go	0.00%	18 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1767      +/-   ##
==========================================
- Coverage   67.01%   66.98%   -0.04%     
==========================================
  Files         219      219              
  Lines       22616    22632      +16     
==========================================
+ Hits        15157    15159       +2     
- Misses       6691     6705      +14     
  Partials      768      768              

Flag	Coverage Δ
integration-test	54.82% <ø> (+0.30%)	⬆️
k8s-integration-test	53.02% <ø> (+0.10%)	⬆️
oats-test	34.33% <ø> (+0.05%)	⬆️
unittests	43.22% <0.00%> (-0.04%)	⬇️

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[mariomac]

I don't get why we need removing the env package (increasing our code surface instead of relying on a stable library that is used in other parts of our code).

If you want to build beyla_genfiles, you can just do, from the project root:

go build -o beyla_genfiles cmd/beyla-genfiles/beyla_genfiles.go

Which already contains the go.mod and vendored dependencies.

[mariomac]

You probably can just copy the whole project, build the project with:

go build -o beyla_genfiles cmd/beyla-genfiles/beyla_genfiles.go

Then, below, instead of FROM base AS builder, do something like:

FROM alpine
COPY --from=base /path/beyla_genfiles .

[mariomac]

Actually you should also move this to the FROM alpine section:

RUN apk add clang llvm19 curl
RUN apk cache purge

And copy the bpf2go command also here.

[mariomac]

Maybe then is simpler to just keep it as you have it now 🤣

[rafaelroquetto]

Hehee nah, that (having an intermediate step and copying the resulting artefacts as you suggest) makes sense indeed. I will look into it.

So, with regards to the dependency on the env package, it was mostly because Alloy does:

go run github.com/grafana/beyla/v2/cmd/beyla-genfiles@main

was giving me issues (the go tool was complaining it could not pull the env dependency). Let me run another tests with the dependency back in place and see how it goes.

[rafaelroquetto]

@mariomac ok I've updated the PR, seems to work for Alloy - I've incorporated all of your suggestions (hopefully, let me know if I missed anything) and it looks better now IMHO.