build-engine.sh fails to build with default values

[brianjjones]

Using the latest Ubuntu, the build-engine.sh script is failing to build with the following error:

Error running mach:

['bootstrap', '--application-choice=js']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.
You can invoke |./mach busted| to check if this issue is already on file. If it
isn't, please use |./mach busted file bootstrap| to report it. If |./mach busted| is
misbehaving, you can also inspect the dependencies of bug 1543241.

If filing a bug, please include the full output of mach, including this error
message.

[william-stacken]

Had the same problem, for me switching to using this fork made the build succeed at least. Maybe it helps?
https://github.com/fastly/spidermonkey-wasi-embedding