[Issue 18120] Document setting DRT options via the environment

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18120

berni44 <bugzilla at d-ecke.de> changed:

           What    |Removed                     |Added
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                 CC|                            |b2.temp at gmx.com

--- Comment #7 from berni44 <bugzilla at d-ecke.de> ---
*** Issue 19951 has been marked as a duplicate of this issue. ***

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