Fails to convert BusyBox based images

[ryanolson]

Singularity: sexec (U=0,P=189)> Command=exec, Container=/tmp/jinja-2016-11-01-68a7b91a1cb0.img, CWD=/, Arg1=/bin/sh
find: unrecognized: -executable
BusyBox v1.24.2 (2016-11-01 12:56:05 GMT) multi-call binary.

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

Failure at: https://github.com/singularityware/docker2singularity/blob/master/docker2singularity.sh#L149

BusyBox's find has the following options:

BusyBox v1.24.2 (2016-11-01 12:56:05 GMT) 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
	-delete		Delete current file/directory. Turns on -depth option

[chrisgorgo]

Fixed via #11