Merge pull request #4615 from urbit/jb/darwin-fsync

build: patch lmdb to use F_FULLFSYNC on darwin

nix/overlays/native.nix

@@ -25,4 +25,11 @@ in {
     ldapSupport = false;
     brotliSupport = false;
   };
+
+  lmdb = prev.lmdb.overrideAttrs (attrs: {
+    patches =
+      optionalList attrs.patches ++ prev.lib.optional prev.stdenv.isDarwin [
+        ../pkgs/lmdb/darwin-fsync.patch
+      ];
+  });
 }

nix/pkgs/lmdb/darwin-fsync.patch

@@ -0,0 +1,13 @@
+diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
+index fe65e30..0070215 100644
+--- a/libraries/liblmdb/mdb.c
++++ b/libraries/liblmdb/mdb.c
+@@ -2526,7 +2526,7 @@ mdb_env_sync(MDB_env *env, int force)
+ 					rc = ErrCode();
+ 			} else
+ #endif
+-			if (MDB_FDATASYNC(env->me_fd))
++			if (fcntl(env->me_fd, F_FULLFSYNC, 0))
+ 				rc = ErrCode();
+ 		}
+ 	}