+++ src/spawn-posix.c	2024-06-21 10:44:49.676834437 +0200
+++ src/spawn-posix.c	2024-06-21 10:45:09.008841639 +0200
@@ -57,6 +57,8 @@
 
 #include "gpgrt-int.h"
 
+/* (Only glibc's unistd.h declares this iff _GNU_SOURCE is used.)  */
+extern char **environ;
 
 /* Definition for the gpgrt_spawn_actions_t.  Note that there is a
  * different one for Windows.  */