Otherwise doesn't compile with -fcommon.

diff -upr mailutils-3.9.orig/imap4d/imap4d.h mailutils-3.9/imap4d/imap4d.h
--- mailutils-3.9.orig/imap4d/imap4d.h	2021-07-10 14:39:56.469994975 +0200
+++ mailutils-3.9/imap4d/imap4d.h	2021-07-10 14:41:29.953368933 +0200
@@ -229,8 +229,6 @@ extern struct mu_tls_config global_tls_c
 extern int test_mode;
 extern int silent_expunge;
 
-int tls_available;
-
 /* Input functions */
 extern mu_stream_t iostream;
 extern int  io_untagged_response (int, const char *, ...) MU_PRINTFLIKE(2,3);
diff -upr mailutils-3.9.orig/lib/tcpwrap.h mailutils-3.9/lib/tcpwrap.h
--- mailutils-3.9.orig/lib/tcpwrap.h	2021-07-10 14:39:56.526661667 +0200
+++ mailutils-3.9/lib/tcpwrap.h	2021-07-10 14:40:13.370002323 +0200
@@ -17,7 +17,7 @@
 #include <mailutils/types.h>
 
 extern int mu_tcp_wrapper_enable;
-const char *mu_tcp_wrapper_daemon;
+extern const char *mu_tcp_wrapper_daemon;
 extern int mu_tcpwrapper_access (int fd);
 extern void mu_tcpwrapper_cfg_init (void);
 extern int mu_tcp_wrapper_prefork (int fd,