add -s and -w flags to the go_binary linkopts

[inteon]

What this PR does / why we need it:
Based on https://blog.filippo.io/shrink-your-go-binaries-with-this-one-weird-trick/, adding -s and -w flags as go_binary linkops arguments reduces the binary size.

From the article:

Interestingly, what gets stripped is only the DWARF tables needed for debuggers, not the annotations needed for stack traces, so our panics are still readable!

The cert-manager kubectl plugin's size shrinks from 68M to 43M.

Kubernetes also applies these flags when compiling their binaries; https://github.com/kubernetes/kubernetes/blob/1861e4756df1818a2d4ca60c869780bf742fff6b/hack/lib/golang.sh#L798-L804.

Release note:

reduce binary sizes by adding "-s -w" as ldflags

/kind feature

[jetstack-bot]

Hi @inteon. Thanks for your PR.

I'm waiting for a jetstack or cert-manager member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[wallrj]

/ok-to-test

[inteon]

• ref: Basic install functionality for kubectl plugin #4138

[jakexks]

/lgtm

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: inteon, jakexks

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [jakexks]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[irbekrm]

We have an internal project where we create an alternative build of cert-manager linked against some C libraries. One of the checks that verify that build tests that it has been linked against the correct libraries etc (using goversion and go tool nm).
This PR has removed the debugging information, so the checks no longer work:

go tool nm com_github_jetstack_cert_manager/cmd/acmesolver/acmesolver_/acmesolver 
reading com_github_jetstack_cert_manager/cmd/acmesolver/acmesolver_/acmesolver: no symbol section
reading com_github_jetstack_cert_manager/cmd/acmesolver/acmesolver_/acmesolver: no symbols

We don't really have a feasible alternative way to do those tests now.
Would it be possible to either only remove the debugging info for the kubectl plugin (the internal project only needs server images), or alternatively parameterize building with these flags @inteon ?