environ needs to be declared.

--- libgpg-error-1.50/src/spawn-posix.c.orig	2024-06-19 09:33:41.000000000 +0200
+++ libgpg-error-1.50/src/spawn-posix.c	2024-06-25 19:54:14.709742742 +0200
@@ -57,6 +57,7 @@
 
 #include "gpgrt-int.h"
 
+extern char **environ;
 
 /* Definition for the gpgrt_spawn_actions_t.  Note that there is a
  * different one for Windows.  */