Correctly forward the value of --depwarn to the test subprocess

[DilumAluthge]

Before this PR:

Value provided to --depwarn by user	Value passed to test subprocess
error	error
yes	yes
no	yes

After this PR:

Value provided to --depwarn by user	Value passed to test subprocess
error	error
yes	yes
no	no

[DilumAluthge]

Since this is a bugfix, would it be possible to backport this PR to Julia 1.5.1?

[fredrikekre]

The current behaviour is expected, cf. #1763. I have meant to fix JLOptions but forgot about it. I will put it on my list.

[DilumAluthge]

The current behaviour is expected, cf. #1763. I have meant to fix JLOptions but forgot about it. I will put it on my list.

I see. Once you fix JLOptions, will explicitly passing --depwarn=no be passed to the subprocess?

[fredrikekre]

Yea. The problem right now is that we can't see the difference between --depwarn=no and not specifying at all.

[DilumAluthge]

Ok cool, I'll close this in favor of the fix you describe.