build: fix missing include

Fix a build failure:

virt-host-validate.c: In function 'main':
virt-host-validate.c:82:5: error: implicit declaration of function 'setlocale' [-Werror=implicit-function-declaration]
virt-host-validate.c:82:5: error: nested extern declaration of 'setlocale' [-Werror=nested-externs]
virt-host-validate.c:82:20: error: 'LC_ALL' undeclared (first use in this function)

* tools/virt-host-validate.c: Add <locale.h>.
* .gitignore: Ignore built executable.

.gitignore

@@ -79,6 +79,7 @@
 /tests/qemuxmlnstest
 /tests/shunloadtest
 /tests/virhashtest
+/tools/virt-host-validate
 /update.log
 Makefile
 Makefile.in

tools/virt-host-validate.c

@@ -25,6 +25,7 @@
 #include <stdlib.h>
 #include <gettext.h>
 #include <getopt.h>
+#include <locale.h>
 
 #include "internal.h"
 #include "configmake.h"