Fix #6377 Drop support of Cabal < 2.2

ChangeLog.md

@@ -10,6 +10,10 @@ Major changes:
 
 Behavior changes:
 
+* Stack uses the version of the Cabal package that comes with the specified
+  version of GHC. Stack no longer supports such Cabal versions before 2.2, which
+  came with versions of GHC before 8.4.
+
 Other enhancements:
 
 * In YAML configuration files, the `msys-environment` key is introduced to

src/Stack/Build.hs

@@ -83,14 +83,17 @@ instance Pretty CabalVersionPrettyException where
     "[S-5973]"
     <> line
     <> fillSep
-         [ flow "Stack does not support Cabal versions before 1.24, but \
-                \version"
+         [ flow "Stack builds with the version of the Cabal package that comes \
+                \with the specified version of GHC. However, Stack no longer \
+                \supports such Cabal versions before 2.2. Version"
          , fromString $ versionString cabalVer
-         , flow "was found. To fix this, consider updating the snapshot to"
-         , style Shell "lts-7.0"
-         , flow "or later or to"
-         , style Shell "nightly-2016-05-26"
-         , flow "or later."
+         , flow "was found. To fix this, either use Stack 2.15.1 or earlier or \
+                \use a snapshot that specifies a version of GHC that is 8.4 or \
+                \later. Stackage LTS Haskell 12.0"
+         , parens (style Shell "lts-12.0")
+         , flow "or later or Nightly 2018-03-13"
+         , parens (style Shell "nightly-2018-03-13")
+         , flow "or later specify such GHC versions."
          ]
 
 instance Exception CabalVersionPrettyException
@@ -221,7 +224,7 @@ justLocals =
 checkCabalVersion :: HasEnvConfig env => RIO env ()
 checkCabalVersion = do
   cabalVer <- view cabalVersionL
-  when (cabalVer < mkVersion [1, 24]) $
+  when (cabalVer < mkVersion [2, 2]) $
     prettyThrowM $ CabalVersionNotSupported cabalVer
 
 -- | See https://github.com/commercialhaskell/stack/issues/1198.

src/Stack/Build/ExecuteEnv.hs

@@ -14,7 +14,6 @@ module Stack.Build.ExecuteEnv
   , withSingleContext
   , ExcludeTHLoading (..)
   , KeepOutputOpen (..)
-  , ExecutableBuildStatus (..)
   , OutputType (..)
   ) where
 
@@ -113,12 +112,6 @@ import           System.Environment ( lookupEnv )
 import           System.FileLock
                    ( SharedExclusive (..), withFileLock, withTryFileLock )
 
--- | Has an executable been built or not?
-data ExecutableBuildStatus
-  = ExecutableBuilt
-  | ExecutableNotBuilt
-  deriving (Eq, Ord, Show)
-
 data ExecuteEnv = ExecuteEnv
   { installLock    :: !(MVar ())
   , buildOpts      :: !BuildOpts