Include dist/build/autogen dir in the -I search list for c-sources.
Include dist/build/autogen dir in the -I search list for c-sources.

Fixes #1351.

valderman/cabal,Peaker/cabal,fugyk/cabal,christiaanb/cabal,ian-ross/cabal,gbaz/cabal,lukexi/cabal,trskop/cabal,kolmodin/cabal,Peaker/cabal,thoughtpolice/cabal,Helkafen/cabal,christiaanb/cabal,eric-stanley/cabal,fpco/cabal,mmakowski/cabal,triplepointfive/cabal,ghc-android/cabal,garetxe/cabal,garetxe/cabal,mydaum/cabal,seereason/cabal,kosmikus/cabal,Heather/cabal,headprogrammingczar/cabal,corngood/cabal,seereason/cabal,headprogrammingczar/cabal,fpco/cabal,sopvop/cabal,kolmodin/cabal,plumlife/cabal,thomie/cabal,gridaphobe/cabal,x-y-z/cabal,typelead/epm,gbaz/cabal,thomie/cabal,anton-dessiatov/cabal,anton-dessiatov/cabal,bennofs/cabal,thoughtpolice/cabal,lukexi/cabal,valderman/cabal,martinvlk/cabal,sopvop/cabal,mightybyte/cabal,ghc-android/cabal,martinvlk/cabal,beni55/cabal,eric-stanley/cabal,mightybyte/cabal,mmakowski/cabal,trskop/cabal,themoritz/cabal,rimmington/cabal,ian-ross/cabal,enolan/cabal,gridaphobe/cabal,rimmington/cabal,Helkafen/cabal,edsko/cabal,mydaum/cabal,bennofs/cabal,plow-technologies/cabal,kosmikus/cabal,x-y-z/cabal,plumlife/cabal,fugyk/cabal,themoritz/cabal,triplepointfive/cabal,randen/cabal,enolan/cabal,corngood/cabal,themoritz/cabal,Heather/cabal,typelead/epm,edsko/cabal,plow-technologies/cabal,sopvop/cabal,beni55/cabal,randen/cabal