Makefile.gen.go: -trimpath for binary size and reproducibility

[lyind]

Summary

Adds the -trimpath flag to the generated Makefile for Go projects.

Go's -trimpath feature removes the local segments from dependency paths when building. This can reduce binary size by megabytes (for some projects) and generally aids reproducability.

This is the help entry for the compiler feature:

	-trimpath
		remove all file system paths from the resulting executable.
		Instead of absolute file system paths, the recorded file names
		will begin either a module path@version (when using modules),
		or a plain import path (when using the standard library, or GOPATH).

The feature should be stable, at least since Go1.18, and a handful of our projects are already using it.

I could find only one known issue when using the feature: LDFLAGS are currently not retained, e.g. not displayed in go version -m {SOME_BINARY}. However, this should mostly matter when enabling CGO, which our Makefiles explicitly disable.

EDIT: I stole this trick from here: gohugoio/hugo#12406 (comment)

Checklist

• Update changelog in CHANGELOG.md.

[lyind]

Successfully tested devctl on devctl via:

$ make
$ ls -al devctl*
-rwxr-xr-x  1 lyind lyind 23375604 Jul 15 13:35 devctl
-rwxr-xr-x  1 lyind lyind 23375604 Jul 15 13:35 devctl-v-linux-amd64
$ ./devctl gen makefile --flavour generic --language go .
$ rm -rf devctl*
$ make
$ ls -al devctl*
-rwxr-xr-x 1 lyind lyind 23305922 Jul 15 13:40 devctl
-rwxr-xr-x 1 lyind lyind 23305922 Jul 15 13:40 devctl-v-linux-amd64
$ ./devctl version
Version:        6.26.5-dev
Git Commit:     11f7544be3e5d90058c6bc253e18ae191f653f3c
Go Version:     go1.22.5
OS / Arch:      linux / amd64
Source:         https://github.com/giantswarm/devctl
$ git checkout -f
$ ./devctl gen makefile --flavour generic --language go .
$ git diff
# matches expected output: devctl seems to work

[lyind]

Why does the devctl build on CircleCI fail, is this related?
https://app.circleci.com/pipelines/github/giantswarm/devctl/3727/workflows/09cf2546-a72f-4f5f-b49a-338dd9eb8bae/jobs/6607