cosign: use buildFlagsArray

[06kellyjac]

Motivation for this change

Bump cosign to 0.3.1 Bump already done, details below still apply to what was changed in #120029

Add ldflags to make the release smaller (21 MB -> 19 MB) and version info

The upstream release looks like follows:

GitVersion:    v0.3.1
GitCommit:     76fde761a4e016c57293113ee1362f1c24a647cb
GitTreeState:  clean
BuildDate:     '2021-04-20T22:40:17Z'
GoVersion:     go1.16.3
Compiler:      gc
Platform:      linux/amd64

Left out the other parts that are commonly skipped in nixpkgs like date etc as they're better left as the default

GitVersion:    v0.3.1
GitCommit:     unknown
GitTreeState:  unknown
BuildDate:     unknown
GoVersion:     go1.16.3
Compiler:      gc
Platform:      linux/amd64

Move the ldflags change to set buildArrayFlags directly within bash. I was going to link the linter that catches this & the reason behind this change but I can't find it now 🙃 @SuperSandro2000 do you remember?

I've also added myself as a maintainer if you dont mind @LeSuisse

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[LeSuisse]

Done in #120029

I've also added myself as a maintainer if you dont mind @LeSuisse

Not at all 👍

[06kellyjac]

Ah sorry, I had a look for the PR but I missed it 😅
I'll rebase now

[LeSuisse]

Is there a difference with buildFlagsArray?

It seems the documentation recommends its usage:

nixpkgs/doc/languages-frameworks/go.section.md

Lines 115 to 132 in 80b3950

	### `buildFlagsArray` and `buildFlags`: {#ex-goBuildFlags-noarray}
	These attributes set build flags supported by `go build`. We recommend using `buildFlagsArray`. The most common use case of these attributes is to make the resulting executable aware of its own version. For example:
	```nix
	buildFlagsArray = [
	# Note: single quotes are not needed.
	"-ldflags=-X main.Version=${version} -X main.Commit=${version}"
	];
	```
	```nix
	buildFlagsArray = ''
	-ldflags=
	-X main.Version=${version}
	-X main.Commit=${version}
	'';
	```

[SuperSandro2000]

See https://github.com/jtojnar/nixpkgs-hammering/blob/master/explanations/no-flags-array.md

[LeSuisse]

Thanks for the explanation, should not the Go documentation be updated?

[Mic92]

Yes. It should be.