Forward SOURCE_DATE_EPOCH to embedded k8s binaries

[twz123]

Description

Make it possible for embedded binaries to pick up the SOURCE_DATE_EPOCH with which k0s is built. If supported, the embedded binaries will display the same build date as the k0s binary.

Currently, only Kubernetes binaries will get the timestamp. It still needs to be checked what other binaries embed the build date.

Also remove some Go build flags that get added by default in the Kubernetes build.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

• Manual test
• Auto test added

Checklist:

• My code follows the style guidelines of this project
• My commit messages are signed-off
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[juanluisvaladas]

Is this a deliberate change or is something that you commited accidentally? I'm not against it but I find this line surprising.

[twz123]

Actually, this prints out the arguments for the build, which is quite handy and is what I used to verify that the build picks up a custom SOURCE_DATE_EPOCH:

https://github.com/k0sproject/k0s/actions/runs/6378582878/job/17309435491?pr=3542#step:7:11718

Building binaries with GCFLAGS=all=-trimpath=/go/src/github.com/kubernetes/kubernetes/_output/local/go/src/k8s.io/kubernetes ASMFLAGS=all=-trimpath=/go/src/github.com/kubernetes/kubernetes/_output/local/go/src/k8s.io/kubernetes LDFLAGS=all=-X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.buildDate=2023-10-02T09:52:01Z' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.buildDate=2023-10-02T09:52:01Z' -X 'k8s.io/client-go/pkg/version.buildDate=2023-10-02T09:52:01Z' -X 'k8s.io/component-base/version.buildDate=2023-10-02T09:52:01Z' -X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.gitCommit=89a4ea3e1e4ddd7f7572286090359983e0387b2f' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.gitCommit=89a4ea3e1e4ddd7f7572286090359983e0387b2f' -X 'k8s.io/client-go/pkg/version.gitCommit=89a4ea3e1e4ddd7f7572286090359983e0387b2f' -X 'k8s.io/component-base/version.gitCommit=89a4ea3e1e4ddd7f7572286090359983e0387b2f' -X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.gitTreeState=clean' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.gitTreeState=clean' -X 'k8s.io/client-go/pkg/version.gitTreeState=clean' -X 'k8s.io/component-base/version.gitTreeState=clean' -X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.gitVersion=v1.28.2+k0s' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.gitVersion=v1.28.2+k0s' -X 'k8s.io/client-go/pkg/version.gitVersion=v1.28.2+k0s' -X 'k8s.io/component-base/version.gitVersion=v1.28.2+k0s' -X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.gitMajor=1' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.gitMajor=1' -X 'k8s.io/client-go/pkg/version.gitMajor=1' -X 'k8s.io/component-base/version.gitMajor=1' -X 'k8s.io/kubernetes/vendor/k8s.io/client-go/pkg/version.gitMinor=28' -X 'k8s.io/kubernetes/vendor/k8s.io/component-base/version.gitMinor=28' -X 'k8s.io/client-go/pkg/version.gitMinor=28' -X 'k8s.io/component-base/version.gitMinor=28' -extldflags=-static -s -w