From 17eb3545906d21f2ed18f0f0f917a4638f12ef6c Mon Sep 17 00:00:00 2001
From: Charles Hall <charles@computer.surgery>
Date: Sun, 5 May 2024 00:23:36 -0700
Subject: [PATCH] prevent bindgen and dependents from building twice

See also <https://crane.dev/faq/rebuilds-bindgen.html>.
---
 nix/pkgs/default/default.nix | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/nix/pkgs/default/default.nix b/nix/pkgs/default/default.nix
index 8cfeac8e..d5accf32 100644
--- a/nix/pkgs/default/default.nix
+++ b/nix/pkgs/default/default.nix
@@ -1,6 +1,7 @@
 # Dependencies (keep sorted)
 { craneLib
 , inputs
+, jq
 , lib
 , pkgsBuildHost
 , rocksdb
@@ -21,6 +22,7 @@ let
       };
     in
     {
+      NIX_OUTPATH_USED_AS_RANDOM_SEED = "randomseed";
       CARGO_PROFILE = profile;
       ROCKSDB_INCLUDE_DIR = "${rocksdb'}/include";
       ROCKSDB_LIB_DIR = "${rocksdb'}/lib";
@@ -63,6 +65,12 @@ let
       # weirdness", pkgs.rustPlatform.bindgenHook on its own doesn't quite do the
       # right thing here.
       pkgsBuildHost.rustPlatform.bindgenHook
+
+      # We don't actually depend on `jq`, but crane's `buildPackage` does, but
+      # its `buildDepsOnly` doesn't. This causes those two derivations to have
+      # differing values for `NIX_CFLAGS_COMPILE`, which contributes to spurious
+      # rebuilds of bindgen and its depedents.
+      jq
     ];
   };
 in