new Error().stack is an Array

[lauriro]

Although Error#stack is a non-standard property,
it would be nice to follow other implementations
and return a String instead of Array.

var err = new Error("Er")
print(typeof err.stack, Array.isArray(err.stack))
// node returns: string false
// jerry returns: object true

Just message + stack joined with newline would be enough as all stack using libraries does expect different format on different environments.

Linux
commit bbb5c91
python tools/build.py --line-info=ON