Fix postgresql musl: clear disallowedReferences for cross-compilation

postgresql/generic.nix sets disallowedReferences = [ stdenv'.cc ] which
scans all outputs for references to the C compiler after build phases
complete. For musl cross-compilation, .pc files or .la files may retain
references to the cross-compiler toolchain path, causing the check to
fail silently — all build phases complete successfully with no error in
the log, but the build is recorded as failed.

This explains why postgresql-musl builds consistently "succeed" (all
phases including fixup and stripping complete) but are recorded as
failures on every builder, even with 400+ GB free disk space.

Author: angerman

flake.nix

@@ -162,6 +162,13 @@
              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 = [];
            });
          });
        };