DMD installer should set up PATH in the same order as it was before reinstall

[dlangBugzillaToGithub]

Andrej Mitrovic (@AndrejMitrovic) reported this on 2023-01-19T16:53:17Z

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

Description

It seems that reinstalling DMD on Windows will cause it to first uninstall and remove DMD from PATH, and then install it and add DMD to PATH as the *last* entry.

This can cause unexpected problems, for example:

- If there is no user-provided dub settings file (https://dub.pm/settings)
- And if another D compiler is installed and is in PATH, e.g. LDC
- And if the DMD was in PATH before LDC

Then after installing a new version of DMD via the installer the LDC compiler will be picked up by default by DUB.

Of course one can set up the default with https://dub.pm/settings, but the user may not be aware of that.