Always set -dynamic-too

This improves Nix compatibility without changing Stack or Cabal
compatibility. See #728.

release-8.2.nix

@@ -62,14 +62,6 @@ let
       ihaskell       = nixpkgs.haskell.lib.overrideCabal (
                        self.callCabal2nix "ihaskell"          ihaskell-src       {}) (_drv: {
         postPatch = let
-          # Nix-built IHaskell expects to load a *.dyn_o file instead of *.o,
-          # see https://github.com/gibiansky/IHaskell/issues/728
-          original = ''
-            setSessionDynFlags
-                  flags'';
-          replacement = ''
-            setSessionDynFlags $ flip gopt_set Opt_BuildDynamicToo
-                  flags'';
           # The tests seem to 'buffer' when run during nix-build, so this is
           # a throw-away test to get everything running smoothly and passing.
           originalTest = ''
@@ -80,8 +72,6 @@ let
                   let throwAway string _ = evaluationComparing (const $ shouldBe True True) string
                   in throwAway "True" ["True"]'';
         in ''
-          substituteInPlace ./src/IHaskell/Eval/Evaluate.hs --replace \
-            '${original}' '${replacement}'
           substituteInPlace ./src/tests/IHaskell/Test/Eval.hs --replace \
             '${originalTest}' '${replacementTest}'
         '';

release.nix

@@ -40,14 +40,6 @@ let
       ihaskell       = nixpkgs.haskell.lib.overrideCabal (
                        self.callCabal2nix "ihaskell"       ihaskell-src       {}) (_drv: {
         postPatch = let
-          # Nix-built IHaskell expects to load a *.dyn_o file instead of *.o,
-          # see https://github.com/gibiansky/IHaskell/issues/728
-          original = ''
-            setSessionDynFlags
-                  flags'';
-          replacement = ''
-            setSessionDynFlags $ flip gopt_set Opt_BuildDynamicToo
-                  flags'';
           # The tests seem to 'buffer' when run during nix-build, so this is
           # a throw-away test to get everything running smoothly and passing.
           originalTest = ''
@@ -58,8 +50,6 @@ let
                   let throwAway string _ = evaluationComparing (const $ shouldBe True True) string
                   in throwAway "True" ["True"]'';
         in ''
-          substituteInPlace ./src/IHaskell/Eval/Evaluate.hs --replace \
-            '${original}' '${replacement}'
           substituteInPlace ./src/tests/IHaskell/Test/Eval.hs --replace \
             '${originalTest}' '${replacementTest}'
         '';

src/IHaskell/Eval/Evaluate.hs

@@ -1080,7 +1080,7 @@ doLoadModule name modName = do
     -- Compile loaded modules.
     flags <- getSessionDynFlags
     errRef <- liftIO $ newIORef []
-    setSessionDynFlags
+    setSessionDynFlags $ flip gopt_set Opt_BuildDynamicToo
       flags
         { hscTarget = objTarget flags
 #if MIN_VERSION_ghc(8,0,0)