Add ability to not overwrite prompt (PS1)

[dlangBugzillaToGithub]

Andrej Mitrovic (@AndrejMitrovic) reported this on 2023-02-05T01:57:39Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=23670

Description

I like installing the compiler via `curl -fsS https://dlang.org/install.sh | bash -s dmd`, but it's annoying that it overwrites my terminal prompt.

So every time I install it I have to edit the file `vi  ~/dlang/dmd-<release>/activate` and comment out `export PS1="(dmd-2.097.2)${PS1:-}"`.

Can we add the option to skip overwriting PS1?