We default configUserInstall to False so we should not set configPackageDB

because we use the value of configUserInstall to set the default value for
configPackageDB, and any value the user sets will override that.

Distribution/Simple/Setup.hs

@@ -251,7 +251,6 @@ defaultConfigFlags progConf = emptyConfigFlags {
     configOptimization = Flag True,
     configVerbose      = Flag normal,
     configUserInstall  = Flag False,           --TODO: reverse this
-    configPackageDB    = Flag GlobalPackageDB,
     configGHCiLib      = Flag True,
     configSplitObjs    = Flag False -- takes longer, so turn off by default
   }