No entry for "target has libm" in settings file

My Hadrian build is dying with

hadrian: '/home/rae/ghc/ghc/_build/stage0/bin/ghc' exited with an error:
No entry for "target has libm" in
"/home/rae/ghc/ghc/_build/stage0/lib/settings"

The error message is accurate: there is no such entry in the settings file. I have no idea why this is the case.

Building on NixOS with https://github.com/alpmestan/ghc.nix at the current HEAD commit (4e69ca6894fe21bf1c6f4ed98ff406dbf9d6541c). I configured with ./configure $CONFIGURE_ARGS, as ghc.nix asks me to.

Help? Thanks!

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