[Issue 18076] dmd -run should work with `-` (stdin) too

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18076

hsteoh at quickfur.ath.cx changed:

           What    |Removed                     |Added
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           Keywords|                            |pull

--- Comment #1 from hsteoh at quickfur.ath.cx ---
https://github.com/dlang/dmd/pull/7435

Turns out, the code change to implement this is trivial.

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