I've tested locally using a nix environment where the Hadrian default build fails on master. With this patch I successfully built and ran tests for flavours: default, perf, quick, and quickest.
The build failure in question is failing to find libffi when building the default flavour on x86_64 with no system wide libffi installed. The command that fails is when linking the ghc binary. The make build system links the ghc binary with -lffi. On that grounds I would say that D5427 will not solve this issue that this patch does.
Do we know what the actual issue is here?
Yes: Hadrian doesn't build/install libffi correctly and ghc and cabal disagree on the name of the libffi .so file (e.g. cabal expects libCffi-ghc8.7.20181126.so while ghc expects libffi.so).