default.nix: drop rb_setenv for BANDB_PATH

Fixes: "bandb - bandb failure: Unable to open sqlite database: unable to open database file"

default.nix

@@ -8,6 +8,10 @@ stdenv.mkDerivation {
 
   src = ./.;
 
+  patches = [
+    ./patches/bandb-remove-setenv.patch
+  ];
+
   configureFlags = [
     "--enable-epoll"
     "--enable-ipv6"

patches/bandb-remove-setenv.patch

@@ -0,0 +1,12 @@
+diff --git a/src/bandbi.c b/src/bandbi.c
+index 96f65b4..0a85a92 100644
+--- a/src/bandbi.c
++++ b/src/bandbi.c
+@@ -82,7 +82,6 @@ start_bandb(void)
+ 	const char *suffix = "";
+ #endif
+ 
+-	rb_setenv("BANDB_DBPATH", PKGLOCALSTATEDIR "/ban.db", 1);
+ 	if(bandb_path == NULL)
+ 	{
+ 		rb_snprintf(fullpath, sizeof(fullpath), "%s/bandb%s", PKGLIBEXECDIR, suffix);