[Issue 23642] DMD installer should set up PATH in the same order as it was before reinstall

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23642

--- Comment #1 from Andrej Mitrovic <andrej.mitrovich at gmail.com> ---
It was clarified to me that in fact LDC comes with its own distribution of DUB.
So that version was picked first from the PATH, and naturally that version of
DUB prefers LDC by default.

Still the installer should be improved to keep DMD in the same PATH location
compared to other paths.

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