Fix to 02c4ab049: use a weak pointer to the sandbox thread
Fix to 02c4ab049: use a weak pointer to the sandbox thread

Otherwise, the sandbox thread cannot be considered deadlocked by the
RTS, and conc033(ghci) hangs (amongst others).

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