ci: Use busybox utils for one build #17011

To make sure Bitcoin Core can be built with BusyBox, see #16927 (comment)

Concept ACK

Concept ACK

@MarcoFalke I'm guessing there's a reason why we don't wanna add another build?

Yeah, another build means the ci is taking longer. I think using BusyBox on one build that bootstraps from ./depends (with gui and wallet) is sufficient.

Concept ACK - am testing locally.

See here: https://travis-ci.org/MarcoFalke/bitcoin-core/jobs/592530914#L4480

And:

 busybox find --help              
BusyBox v1.27.2 (Ubuntu 1:1.27.2-2ubuntu3.2) multi-call binary.

Usage: find [-HL] [PATH]... [OPTIONS] [ACTIONS]

Search for files and perform actions on them.
First failed action stops processing of current file.
Defaults: PATH is current directory, action is '-print'

	-L,-follow	Follow symlinks
	-H		...on command line only
	-xdev		Don't descend directories on other filesystems
	-maxdepth N	Descend at most N levels. -maxdepth 0 applies
			actions to command line arguments only
	-mindepth N	Don't act on first N levels
	-depth		Act on directory *after* traversing it

Actions:
	( ACTIONS )	Group actions for -o / -a
	! ACT		Invert ACT's success/failure
	ACT1 [-a] ACT2	If ACT1 fails, stop, else do ACT2
	ACT1 -o ACT2	If ACT1 succeeds, stop, else do ACT2
			Note: -a has higher priority than -o
	-name PATTERN	Match file name (w/o directory name) to PATTERN
	-iname PATTERN	Case insensitive -name
	-path PATTERN	Match path to PATTERN
	-ipath PATTERN	Case insensitive -path
	-regex PATTERN	Match path to regex PATTERN
	-type X		File type is X (one of: f,d,l,b,c,...)
	-perm MASK	At least one mask bit (+MASK), all bits (-MASK),
			or exactly MASK bits are set in file's mode
	-mtime DAYS	mtime is greater than (+N), less than (-N),
			or exactly N days in the past
	-mmin MINS	mtime is greater than (+N), less than (-N),
			or exactly N minutes in the past
	-newer FILE	mtime is more recent than FILE's
	-inum N		File has inode number N
	-user NAME/ID	File is owned by given user
	-group NAME/ID	File is owned by given group
	-size N[bck]	File size is N (c:bytes,k:kbytes,b:512 bytes(def.))
			+/-N: file size is bigger/smaller than N
	-links N	Number of links is greater than (+N), less than (-N),
			or exactly N
	-prune		If current file is directory, don't descend into it
If none of the following actions is specified, -print is assumed
	-print		Print file name
	-print0		Print file name, NUL terminated
	-exec CMD ARG ;	Run CMD with all instances of {} replaced by
			file name. Fails if CMD exits with nonzero
	-exec CMD ARG + Run CMD with {} replaced by list of file names

re run ci

Concep ACK, in general it is better to rely on BusyBox rather GNU because GNU has features which other unix systems might not have.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #17041 (ci: Run tests on arm by MarcoFalke)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

Concep ACK, in general it is better to rely on BusyBox rather GNU because GNU has features which other unix systems might not have.

I guess it also reduces the number of packages that need to be built (are you using busybox utils in GUIX @dongcarl?).

Still, we want to run some builds with GNU utilities too, to make sure compatibility is not broken there.

ACK ddddd8961b6209cba1bcabad73916051a99f2025

@laanwj Sure thing but everything which works under busybox will work under GNU but not necessarily vice versa.

@emilengler Is this documented somewhere?

@laanwj Sure thing but everything which works under busybox will work under GNU but not necessarily vice versa.

Even if theoretically true. I don't think any software can ever guarantee to be a strict subset of another.

@MarcoFalke https://www.youtube.com/watch?v=nTCHapo8QFM