Recompilation is a bit broken with hs-boot files

Consider the following 4 modules.

https://gist.github.com/mpickering/7b0e181caab30e265f092f78505a35a2

Recompilation warns about a "missing old dependency" when compiling M despite nothing being changed.

[nix-shell:~/ghc-hash-builds]$ ghci M.hs -fwrite-interface -fno-code
GHCi, version 8.10.2: https://www.haskell.org/ghc/  :? for help
[1 of 4] Compiling O                ( O.hs, nothing )
[2 of 4] Compiling N[boot]          ( N.hs-boot, nothing )
[3 of 4] Compiling N                ( N.hs, nothing )
[4 of 4] Compiling M                ( M.hs, nothing )
Ok, four modules loaded.
*M> :q
[nix-shell:~/ghc-hash-builds]$ ghci M.hs -fwrite-interface  -fno-code
GHCi, version 8.10.2: https://www.haskell.org/ghc/  :? for help
[4 of 4] Compiling M                ( M.hs, nothing ) [missing old dependency]
Ok, four modules loaded.
*M> 

For some reason we don't following boot dependencies in checkForNewHomeDependency which is why the error happens.