texlua os.spawn does not wait

[edocevoli]

Discussed in #1286

^{Originally posted by siepodrop February 14, 2023}
With miktex texlua, os.spawn appears not to wait until the invocation is finished. It does wait in TL texlua. MWE:

kpse.set_program_name('texlua')

print('execute')
cmd = 'pdflatex sample2e'
print(cmd)
rbool, rstring, rnum = os.execute(cmd)
print('|', rbool, '|', rstring, '|', rnum, '|')

cmd = 'pdflatex sample2e'
print('spawn with string argument', cmd)
rbool, rstring, rnum = os.spawn(cmd)
print('|', rbool, '|', rstring, '|', rnum, '|')

cmd = {'pdflatex', 'sample2e'}
print('spawn with table argument', cmd)
rbool, rstring, rnum = os.spawn(cmd)
print('|', rbool, '|', rstring, '|', rnum, '|')
```</div>

[edocevoli]

This has been fixed