haskell.packages.*.system-cxx-std-lib: make sure attr always exists

GHC 9.4 introduced a virtual package for linking against the C++
standard library. Since some packages depend on it when configured with
GHC 9.4 (as hackage2nix does), we need to make sure the attribute exists
or some packages will fail to evaluate. The may still build, even though
there is no shim for lower GHC versions (as far as I know).

1 files changed, 3 insertions, 0 deletions

diff --git a/pkgs/development/haskell-modules/configuration-ghc-8.8.x.nix b/pkgs/development/haskell-modules/configuration-ghc-8.8.x.nix
index e7cb3f23d2df..756b66237e62 100644
--- a/pkgs/development/haskell-modules/configuration-ghc-8.8.x.nix
+++ b/pkgs/development/haskell-modules/configuration-ghc-8.8.x.nix
@@ -46,6 +46,9 @@ self: super: {
   # GHC only bundles the xhtml library if haddock is enabled, check if this is
   # still the case when updating: https://gitlab.haskell.org/ghc/ghc/-/blob/0198841877f6f04269d6050892b98b5c3807ce4c/ghc.mk#L463
   xhtml = if self.ghc.hasHaddock or true then null else self.xhtml_3000_2_2_1;
+  # These core package only exist for GHC >= 9.4. The best we can do is feign
+  # their existence to callPackages, but their is no shim for lower GHC versions.
+  system-cxx-std-lib = null;
 
   # Need the Cabal-syntax-3.6.0.0 fake package for Cabal < 3.8 to allow callPackage and the constraint solver to work
   Cabal-syntax = self.Cabal-syntax_3_6_0_0;