When there are preprocessed non-Hs files, they are added to all -sources

[phadej]

cabal/Cabal/Distribution/Simple/Build.hs

Lines 219 to 228 in ee11888

	extras <- preprocessExtras verbosity comp lbi
	setupMessage' verbosity "Building" (packageId pkg_descr)
	(componentLocalName clbi) (maybeComponentInstantiatedWith clbi)
	let libbi = libBuildInfo lib
	lib' = lib { libBuildInfo = flip addExtraAsmSources extras
	$ flip addExtraCmmSources extras
	$ flip addExtraCxxSources extras
	$ flip addExtraCSources extras
	$ libbi
	}

This is one part of #6377, but is separate issue.