Fix RTD builds using Pixi

[VeckoTheGecko]

Looks like the RTD build is failing with the following error message

Missing configuration option At least one of the following configuration options is required: build.tools or build.commands.

which is quite strange since I pretty much following the docs exactly (docs, readthedocs/readthedocs.org#12155) . I'll post an issue in RTD to update their example and see what they say. Low priority

Originally posted by @VeckoTheGecko in #2244 (comment)