postgresql musl: single output to work around Determinate Nix bug

Multi-output derivations on macOS (APFS) fail to register in the Nix
DB — build completes but outputs remain orphaned. sync-before-registering
= true did not fix this. Merging all outputs into "out" avoids the
multi-output registration path. Consumers only need lib/ and pg_config.

Author: angerman

flake.nix

@@ -162,20 +162,20 @@
              doCheck = false;
              outputChecks = {};
              separateDebugInfo = false;
-             # generic.nix sets disallowedReferences = [ stdenv'.cc ] which
-             # scans outputs for references to the C compiler AFTER all build
-             # phases complete. For musl cross-compilation, .pc files or .la
-             # files may retain references to the cross-compiler, causing a
-             # silent post-fixup failure (all phases complete, no error in
-             # build log, but build recorded as failed).
              disallowedReferences = [];
-             # Force new drv hash to bypass hydra queue runner's persistent
-             # failure cache. Previous builds succeeded but outputs were not
-             # registered in the Nix DB (Determinate Nix orphaned store path
-             # bug). Orphaned paths cleaned and sync-before-registering deployed.
-             preBuild = (old.preBuild or "") + ''
-               # cache breaker v2: sync-before-registering deployed 2026-02-17
-               true
+             # Merge all outputs into "out" to work around Determinate Nix
+             # orphaned store path bug on macOS (APFS). Multi-output derivations
+             # fail to register atomically in the Nix DB — the build completes
+             # but outputs remain orphaned (exist on disk, not valid in DB).
+             # sync-before-registering = true did not fix this. Single-output
+             # avoids the multi-output registration path entirely. Consumers
+             # (haskell.nix libpq) only need lib/ and bin/pg_config anyway.
+             outputs = [ "out" ];
+             # Replace the upstream postInstall which splits outputs and
+             # removes pg_config from $out. We need everything in $out.
+             postInstall = ''
+               make -C src/common pg_config.env
+               install -D src/common/pg_config.env "$out/nix-support/pg_config.env"
              '';
            });
          });