Merge pull request #3765 from peti/re-enable-flexible-defaults

re-enable lambdabot-core, lambdabot-irc-plugins, and their missing dependencies

build-constraints.yaml

@@ -2195,6 +2195,7 @@ packages:
         - cabal2nix
         - cabal2spec
         - distribution-nixpkgs
+        - flexible-defaults
         - funcmp
         - hackage-db
         - hledger-interest
@@ -2204,12 +2205,17 @@ packages:
         - hsyslog
         - jailbreak-cabal
         - json-autotype
-        - lambdabot-core < 0 # GHC 8.4 via random-fu
-        - lambdabot-irc-plugins < 0 # GHC 8.4 via lambdabot-core
+        - lambdabot-core
+        - lambdabot-irc-plugins
         - language-nix
         - logging-facade-syslog
+        - MonadPrompt
         - nix-paths
         - prim-uniq
+        - random-fu
+        - random-source
+        - rvar
+        - SafeSemaphore
         - streamproc
         - titlecase