Reduce binary size using -s -w ldflags

[caxu-rh]

Thank you for contributing to Velero!

Please add a summary of your change

This change adds the Go ldflags -s -w which omits the symbol table and DWARF debugging information from the resulting binaries. The flags are added in GoReleaser configuration, Dockerfile{-Windows}, and the hack/build.sh for consistency. This allows for some reductions in binary size. Note that the size of release tarballs might not change as much (symbol table and DWARF debug info compress well), but the size of the unpacked binary on-disk will see improvements.

From local testing:

os/arch	CGO_ENABLED=0 go build ./cmd/velero/velero.go	CGO_ENABLED=0 go build -ldflags '-s -w' ./cmd/velero/velero.go
darwin/arm64	132M	90M
darwin/amd64	139M	97M
linux/amd64	135M	94M
linux/arm64	126M	87M
linux/arm	124M	86M
linux/ppc64le	131M	92M
linux/s390x	135M	95M
windows/amd64	136M	97M

Does your change fix a particular issue?

This change does not fix a particular issue.

Please indicate you've done the following:

• Accepted the DCO. Commits without the DCO will delay acceptance.
• Created a changelog file (make new-changelog) or comment /kind changelog-not-required on this PR.
• Updated the corresponding documentation in site/content/docs/main.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 60.73%. Comparing base (48e66b1) to head (37d1e9f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9627      +/-   ##
==========================================
- Coverage   60.76%   60.73%   -0.03%     
==========================================
  Files         387      387              
  Lines       36618    36618              
==========================================
- Hits        22250    22241       -9     
- Misses      12773    12781       +8     
- Partials     1595     1596       +1     

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[ywk253100]

Thanks @caxu-rh for the PR!
Based on the size of release tarballs might not change as much (symbol table and DWARF debug info compress well), seems the change has not significantly reduced the size of deliverables.
And without the symbol table, we could not see the function names when the process panics or prints the error message with stack, which impacts the debugging.

[caxu-rh]

seems the change has not significantly reduced the size of deliverables.

Yes, but this should still reduce the size of what users will actually run/install/keep on their disk. You can't execute the binary without unpacking it.

we could not see the function names when the process panics or prints the error message with stack, which impacts the debugging.

I think the function names/stack trace is not impacted by the addition of these flags. For example, I inserted a panic(nil) in pkg/client/factory.go to see how it would look:

panic: panic called with nil argument

goroutine 1 [running]:
github.com/vmware-tanzu/velero/pkg/client.NewFactory(...)
	/Users/caxu/velero/ldflags-s-w/pkg/client/factory.go:91
github.com/vmware-tanzu/velero/pkg/cmd/velero.NewCommand({0x16d1eb3b2, 0x6})
	/Users/caxu/velero/ldflags-s-w/pkg/cmd/velero/velero.go:97 +0x124
main.main()
	/Users/caxu/velero/ldflags-s-w/cmd/velero/velero.go:34 +0x50