haskell.lib.buildFromSdist: add test, fix double-patch

Same issue as buildFromCabalSdist: sdistTarball applies patches via
overrideDerivation, but the patches attribute remained, causing
patchPhase to apply them again.

pkgs/development/haskell-modules/lib/compose.nix

@@ -482,10 +482,11 @@ rec {
     overrideCabal (drv: {
       src = "${sdistTarball pkg}/${pkg.pname}-${pkg.version}.tar.gz";
 
-      # Revising and jailbreaking the cabal file has been handled in sdistTarball
+      # Revising, jailbreaking and patches have been handled in sdistTarball
       revision = null;
       editedCabalFile = null;
       jailbreak = false;
+      patches = [ ];
     }) pkg;
 
   /*

pkgs/test/haskell/cabalSdist/default.nix

@@ -57,4 +57,17 @@ lib.recurseIntoAttrs rec {
         ${lib.getExe localPatchedFromCabalSdist} | grep "Patched" >/dev/null
         touch $out
       '';
+
+  # Test that buildFromSdist (non-cabal-install variant) also respects patches.
+  localPatchedFromSdist = haskell.lib.buildFromSdist localPatched;
+
+  patchRespectedSdist =
+    runCommand "patchRespectedSdist"
+      {
+        nativeBuildInputs = [ localPatchedFromSdist ];
+      }
+      ''
+        ${lib.getExe localPatchedFromSdist} | grep "Patched" >/dev/null
+        touch $out
+      '';
 }