build: fix compilation of virt-login-shell.c

virt-login-shell.c was failing to compile with

CC       virt_login_shell-virt-login-shell.o
virt-login-shell.c: In function 'main':
virt-login-shell.c:205:5: error: implicit declaration of function 'setlocale' [-Werror=implicit-function-declaration]
virt-login-shell.c:205:5: error: nested extern declaration of 'setlocale' [-Werror=nested-externs]
virt-login-shell.c:205:20: error: 'LC_ALL' undeclared (first use in this function)

tools/virt-login-shell.c

@@ -27,6 +27,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <fnmatch.h>
+#include <locale.h>
 
 #include "internal.h"
 #include "virerror.h"