Fix includes (#5980)

Needed on musl.

src/libsystemd/sd-event/test-event.c

@@ -17,6 +17,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <sys/wait.h>
+
 #include "sd-event.h"
 
 #include "fd-util.h"

src/machine/image-dbus.c

@@ -17,6 +17,7 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <sys/file.h>
 #include <sys/mount.h>
 
 #include "alloc-util.h"

src/machine/operation.c

@@ -17,6 +17,8 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <sys/wait.h>
+
 #include "alloc-util.h"
 #include "fd-util.h"
 #include "operation.h"

src/nspawn/nspawn-network.c

@@ -19,6 +19,7 @@
 
 #include <linux/veth.h>
 #include <net/if.h>
+#include <sys/file.h>
 
 #include "libudev.h"
 #include "sd-id128.h"

src/nspawn/nspawn-stub-pid1.c

@@ -18,9 +18,9 @@
 ***/
 
 #include <sys/reboot.h>
-#include <sys/unistd.h>
 #include <sys/wait.h>
 #include <sys/prctl.h>
+#include <unistd.h>
 
 #include "fd-util.h"
 #include "log.h"