check for failed external symbol lookups (partial fix for #5748)
check for failed external symbol lookups (partial fix for #5748)

lukexi/ghc,nkaretnikov/ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc,fmthoma/ghc,tjakway/ghcjvm,nomeata/ghc,vTurbine/ghc,ghc-android/ghc,ghc-android/ghc,ezyang/ghc,sgillespie/ghc,gcampax/ghc,lukexi/ghc-7.8-arm64,GaloisInc/halvm-ghc,acowley/ghc,gridaphobe/ghc,nkaretnikov/ghc,anton-dessiatov/ghc,mfine/ghc,wxwxwwxxx/ghc,christiaanb/ghc,TomMD/ghc,mcschroeder/ghc,ryantm/ghc,acowley/ghc,green-haskell/ghc,mettekou/ghc,sdiehl/ghc,AlexanderPankiv/ghc,bitemyapp/ghc,oldmanmike/ghc,nathyong/microghc-ghc,siddhanathan/ghc,acowley/ghc,nushio3/ghc,holzensp/ghc,lukexi/ghc-7.8-arm64,ghc-android/ghc,anton-dessiatov/ghc,siddhanathan/ghc,acowley/ghc,ml9951/ghc,snoyberg/ghc,jstolarek/ghc,snoyberg/ghc,GaloisInc/halvm-ghc,lukexi/ghc,vTurbine/ghc,da-x/ghc,frantisekfarka/ghc-dsi,ml9951/ghc,anton-dessiatov/ghc,hferreiro/replay,jstolarek/ghc,mcschroeder/ghc,nushio3/ghc,gridaphobe/ghc,vikraman/ghc,da-x/ghc,nathyong/microghc-ghc,christiaanb/ghc,TomMD/ghc,AlexanderPankiv/ghc,nomeata/ghc,sgillespie/ghc,TomMD/ghc,oldmanmike/ghc,mettekou/ghc,anton-dessiatov/ghc,holzensp/ghc,acowley/ghc,hferreiro/replay,anton-dessiatov/ghc,bitemyapp/ghc,christiaanb/ghc,shlevy/ghc,shlevy/ghc,tibbe/ghc,ekmett/ghc,mettekou/ghc,sgillespie/ghc,tjakway/ghcjvm,vTurbine/ghc,wxwxwwxxx/ghc,AlexanderPankiv/ghc,forked-upstream-packages-for-ghcjs/ghc,lukexi/ghc,elieux/ghc,green-haskell/ghc,gridaphobe/ghc,tjakway/ghcjvm,ghc-android/ghc,oldmanmike/ghc,shlevy/ghc,green-haskell/ghc,nushio3/ghc,mettekou/ghc,gcampax/ghc,elieux/ghc,vikraman/ghc,anton-dessiatov/ghc,oldmanmike/ghc,forked-upstream-packages-for-ghcjs/ghc,sdiehl/ghc,mcschroeder/ghc,ghc-android/ghc,nathyong/microghc-ghc,AlexanderPankiv/ghc,fmthoma/ghc,wxwxwwxxx/ghc,TomMD/ghc,vikraman/ghc,ml9951/ghc,nushio3/ghc,sdiehl/ghc,tibbe/ghc,olsner/ghc,hferreiro/replay,tjakway/ghcjvm,sdiehl/ghc,green-haskell/ghc,frantisekfarka/ghc-dsi,nomeata/ghc,da-x/ghc,vTurbine/ghc,ryantm/ghc,elieux/ghc,tibbe/ghc,snoyberg/ghc,olsner/ghc,tibbe/ghc,gcampax/ghc,lukexi/ghc-7.8-arm64,mfine/ghc,siddhanathan/ghc,bitemyapp/ghc,nkaretnikov/ghc,ekmett/ghc,elieux/ghc,nathyong/microghc-ghc,shlevy/ghc,snoyberg/ghc,TomMD/ghc,christiaanb/ghc,urbanslug/ghc,vikraman/ghc,elieux/ghc,spacekitteh/smcghc,siddhanathan/ghc,ezyang/ghc,mettekou/ghc,forked-upstream-packages-for-ghcjs/ghc,frantisekfarka/ghc-dsi,nomeata/ghc,ml9951/ghc,lukexi/ghc-7.8-arm64,christiaanb/ghc,spacekitteh/smcghc,gcampax/ghc,mcschroeder/ghc,lukexi/ghc,da-x/ghc,lukexi/ghc,vTurbine/ghc,lukexi/ghc-7.8-arm64,sgillespie/ghc,anton-dessiatov/ghc,olsner/ghc,jstolarek/ghc,mettekou/ghc,urbanslug/ghc,ezyang/ghc,holzensp/ghc,nkaretnikov/ghc,da-x/ghc,elieux/ghc,nkaretnikov/ghc,green-haskell/ghc,sgillespie/ghc,mfine/ghc,ml9951/ghc,nkaretnikov/ghc,snoyberg/ghc,tjakway/ghcjvm,tjakway/ghcjvm,tibbe/ghc,oldmanmike/ghc,olsner/ghc,mfine/ghc,jstolarek/ghc,ezyang/ghc,gridaphobe/ghc,GaloisInc/halvm-ghc,sdiehl/ghc,siddhanathan/ghc,ghc-android/ghc,urbanslug/ghc,mcschroeder/ghc,TomMD/ghc,hferreiro/replay,siddhanathan/ghc,GaloisInc/halvm-ghc,frantisekfarka/ghc-dsi,nomeata/ghc,hferreiro/replay,ryantm/ghc,spacekitteh/smcghc,nushio3/ghc,ezyang/ghc,mfine/ghc,mcschroeder/ghc,fmthoma/ghc,holzensp/ghc,mfine/ghc,siddhanathan/ghc,wxwxwwxxx/ghc,sdiehl/ghc,ryantm/ghc,mettekou/ghc,snoyberg/ghc,gcampax/ghc,ml9951/ghc,TomMD/ghc,oldmanmike/ghc,ekmett/ghc,spacekitteh/smcghc,hferreiro/replay,elieux/ghc,AlexanderPankiv/ghc,ml9951/ghc,sdiehl/ghc,fmthoma/ghc,bitemyapp/ghc,sgillespie/ghc,olsner/ghc,GaloisInc/halvm-ghc,gridaphobe/ghc,da-x/ghc,christiaanb/ghc,urbanslug/ghc,ml9951/ghc,tjakway/ghcjvm,vTurbine/ghc,fmthoma/ghc,GaloisInc/halvm-ghc,wxwxwwxxx/ghc,acowley/ghc,olsner/ghc,spacekitteh/smcghc,wxwxwwxxx/ghc,olsner/ghc,ekmett/ghc,vTurbine/ghc,snoyberg/ghc,frantisekfarka/ghc-dsi,vikraman/ghc,holzensp/ghc,gcampax/ghc,christiaanb/ghc,ekmett/ghc,nushio3/ghc,nushio3/ghc,forked-upstream-packages-for-ghcjs/ghc,nathyong/microghc-ghc,urbanslug/ghc,gridaphobe/ghc,gridaphobe/ghc,wxwxwwxxx/ghc,ryantm/ghc,ezyang/ghc,sgillespie/ghc,jstolarek/ghc,oldmanmike/ghc,mcschroeder/ghc,fmthoma/ghc,AlexanderPankiv/ghc,ezyang/ghc,urbanslug/ghc,hferreiro/replay,nathyong/microghc-ghc,nkaretnikov/ghc,gcampax/ghc,AlexanderPankiv/ghc,fmthoma/ghc,shlevy/ghc,acowley/ghc,shlevy/ghc,forked-upstream-packages-for-ghcjs/ghc,urbanslug/ghc,vikraman/ghc,GaloisInc/halvm-ghc,da-x/ghc,vikraman/ghc,bitemyapp/ghc,ghc-android/ghc,forked-upstream-packages-for-ghcjs/ghc,mfine/ghc,shlevy/ghc