Add a comment about how to do validate while capturing a debug log, for debugging the build system.
Add a comment about how to do validate while capturing a debug log,
for debugging the build system.

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