Added a further kwarg to PlatformEngines download function

[GhostOfElectric]

Doing in the REPL

@1.11> add Plots

can potentially act differently from doing

using Pkg; Pkg.add("Plots")

because (I think) the downloader parameter isn't present in the PlatformEngines.jl file in the download function.

[cf. Downloads EASY_HOOK regression in v1.11.0

[IanButterworth]

Doing
@1.11> add("Plots")

That's not valid julia pkg mode syntax

[IanButterworth]

Also, please elaborate on "can potentially act differently"

[GhostOfElectric]

Is the link enough detail? This is my first pull request, sorry.

[IanButterworth]

I don't really follow why this is a fix, but I appreciate this is a complicated issue because to properly test the repl mode that is loaded via a repl switch, not using Pkg, julia needs to be built with this version of Pkg.

I'm guessing you haven't done that?

If you have and this is indeed a fix, I think it points to multiple versions of Downloads being loaded by require_stdlib.. but I've not been able to prove that.

[GhostOfElectric]

I haven't done that no, and I can't really, the need to change the easy_hook settings comes from my work's proxy and I can't build Julia there.