[Issue 13989] add system-specific ext to -of parameter if ext is invalid

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13989

--- Comment #2 from bb.temp at gmx.com ---
Your argument doesn't stand. If I follow your logic then in case 2) the
extension shouldn't be added.

Another thing: let's imagine a cross-plateform script for building an
application, if the of parameter contain a dot in its name. On linux the output
file can be executed directly but not under Win.

Maybe should I rephrase my feature request as a proposition for a new switch,
e.g: "-fe" "force standard extension" ?

-fe: under win always add .exe, under nux add nothing
-lib -fe: always add .lib or .a
-shared -fe: always add .dll or .so
etc

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