refactor(compile): add trimpath to compile to remove local paths

[sheldonhull]

• Include trimpath to ensure local filepaths from CI or developer don't get included in the produced artifact.
• This was added in Go 1.13, so not sure if there is something special to handle adding this flag only if go version > 1.13.

Go documentation on this:

-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).

[jaredallard]

I feel like the aqua part should be called out in the title/desc somewhere....

EDIT: Ah, I see, that is from #451 and just wasn't removed when making this PR. I'd suggest cleaning that up :D

[sheldonhull]

My mistake. I did a pr for that but did it on main branch in fork resulting in my new branch including that. I’ll have to separate this out.

[sheldonhull]

@jaredallard reverted back so pr changes are now just this. Not sure about compatibility for prior go versions to 1.13 like I mentioned but otherwise this will be good for privacy. Right now compiled binary includes full path. Cheers

[jaredallard]

Looks reasonable to me :D

[natefinch]

I applied the trimpath change to current master (0953947) and checked compilation, cross-compilation, deterministic generated output, and cache behavior. The main concern is the compatibility impact of making trimpath unconditional, rather than the flag implementation itself. The inline comment describes a reproduced source-relative asset lookup regression. Go-version availability is no longer a concern with the current Go 1.18 minimum.

[natefinch]

Making -trimpath unconditional changes existing magefile behavior with no opt-out. Targets or helper libraries can use runtime.Caller to locate files relative to their source directory. I reproduced a program reading an adjacent asset via filepath.Join(filepath.Dir(file), "asset.txt"): the untrimmed build succeeds when run from another directory, while this build fails with open asset.txt: no such file or directory because the recorded source filename is no longer an absolute filesystem path. This is an inherent tradeoff of trimming paths, not a flag implementation bug. Could we make this opt-in, or provide an explicit opt-out and document the compatibility change, rather than changing all existing magefiles silently?