Can't specify `SplitObjs` with Hadrian build

I'm not sure if this is a documentation issue or the feature is actually missing, but there seems to be no way to specify SplitObjs with the new Hadrian-based build.

https://gitlab.haskell.org/ghc/ghc/-/wikis/building/using has an explanation about that flag, but https://gitlab.haskell.org/ghc/ghc/-/wikis/building/hadrian doesn't mention anything about that.

I built GHC on git head; it looks like SplitObjs is disabled by default.

Is there any way to enable it with Hadrian build? It should be documented in the GHC build instruction.

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