Remove nimble from nim compilation

[arnetheduck]

As of https://github.com/nim-lang/nimble/pull/1131, nimble can build nim - however, as part of building nim-the-compiler, it also builds a toolchain including nimble - this can lead to the user instance of nimble being replaced with the version that gets compiled with nim.

when nimble installs nim as part of the dependencies of a project, it should not compile nimble and other tooling as this makes nimble shell and similar behave inconsistently as nimble gets replaced by a different version.