Conditional Requires in Nimble

[heinthanth]

Hello, this is not an issue. But feature request.

requires "nim >= 1.6.4"
when not defined(noNoise): requires "noise >= 0.1.4"

Can we have this feature? Like if user pass with -d:noNoise, nimble won't download package list, packages, and work without internet access.

[heinthanth]

it's like duplicate to #790 . Same idea.