update build/release process and add static binary builds

[rosskirkpat]

• rework/add build scripts that enable statically linked builds of the flannel-cni plugin binary on linux (all arches) and windows (amd64 only)
• add verification of static builds for linux and windows
• update the go build logic to fail if GOOS is not linux or windows
• update makefile and gh actions to use simplified builds and steps
• automate releases via GH actions
• add a Dockerfile that will build all of the binaries in a reproducible manner for dev/debug purposes
• retain all of the prior image build/publish steps

[rosskirkpat]

I have the flannel cni plugin building as a statically linked binary now on linux/amd64.

make build_linux
CGO_ENABLED=0 GOOS=linux GOARCH=amd64 scripts/build_flannel.sh
Building flannel for linux in amd64

dist/flannel-amd64: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, Go BuildID=mLVLxfqNj4YGYi6HA8Lk/H0AAocC3f3VLIaxfEPEL/Ac0Mx1i37e5OypcAa18d/T1eyQiZ_PX8H71iCUcte, not stripped
verified static links for dist/flannel-amd64

[manuelbuil]

Thanks Ross! We currently have a mismatch in how we are building the "raw" binaries and how we are building the binaries being distributed inside images (target: dist/flannel-$(ARCH)). Could you modify that target too so that they use the script build_flannel.sh please? That way we will have both statically built

[manuelbuil]

Could you adapt .github/workflows/release.yml and .github/workflows/buildTests.yml to the new Makefile please?

[manuelbuil]

Please separate this into two different PRs.

• One building things statically including:

switch to statically linked builds of the flannel-cni plugin binary on linux and windows
add verification of static builds for linux and windows
update the go build logic to fail if GOOS is not linux or windows
update makefile and gh actions to use simplified builds and steps

• One removing all the Docker files:

remove all build and publish steps for images with the exception of the new Dockerfile for building all of the images in a reproducible manner

The second PR requires changes in how flannel is consumed and we will need to bring it up in the bi-weekly meeting

[rosskirkpat]

@Oats87 @luthermonson @manuelbuil @rajatchopra This is ready for review.

[manuelbuil]

Another comment I forgot: I guess we don't need the package version anymore. Could you remove it?

[luthermonson]

@rosskirkpat will drop the version stuff and update the src_dir stuff per @manuelbuil 's request and we will merge this.

[rajatchopra]

/lgtm

[manuelbuil]

@rosskirkpat will drop the version stuff and update the src_dir stuff per @manuelbuil 's request and we will merge this.

And rebasing. There are apparently conflicts :)

[rosskirkpat]

@rosskirkpat will drop the version stuff and update the src_dir stuff per @manuelbuil 's request and we will merge this.

And rebasing. There are apparently conflicts :)

After a rebase, there are no conflicts and I also resolved the remaining feedback.

[manuelbuil]

Thanks Ross!