License addition doesn't work on macOS Big Sur

Version: 5.3.0

When I'm trying to add license.txt it fails with the following message:

✖ Code signing failed. The DMG is fine, just not code signed.
hdiutil: unflatten: verb not recognized
Usage: /usr/bin/hdiutil <verb> <options>
<verb> is one of the following:
help
attach
detach
eject
verify
create
compact
convert
burn
info
checksum
chpass
erasekeys
imageinfo
isencrypted
makehybrid
mount
mountvol
unmount
plugins
resize
segment
pmap
udifderez
udifrez

It seems to be a known issue and here's how it's fixed in electron-builder.

[ardaa]

What is your npm version? Did you try updating npm and electron-builder to the latest version? Seems like an issue with electron-builder.

What is your npm version? Did you try updating npm and electron-builder to the latest version? Seems like an issue with electron-builder.

My npm version is 6.14.8, but I think it's irrelevant, electron-builder is not used in this project anyway I've just used it for the reference.

I believe the problem is in this piece of code:

create-dmg/sla.js

Line 67 in cbabf27

await execa('/usr/bin/hdiutil', ['unflatten', tempDmgPath]);

There's no unflatten verb in hdiutil on macOS Big Sur.

[sindresorhus]

There's a solution in https://stackoverflow.com/a/64836269/64949

Fellow @create-dmg devs have recently added create-dmg/create-dmg@f75cc03 to solve the same issue.

[dxdc]

For a working fix, albeit maybe short-term: #66

[kafeg]

As I understand, alternate solution is to disable license addition in this project and use separate executable to add license from here: https://github.com/argv-minus-one/dmg-license