bus: replace aligned_alloc() with memalign() everywhere

aligned_alloc() is C11 and not available everywhere. Also it would
require us to align the size value. So let's just invoke memalign()
instead, which is universally available and doesn't have any alignment
restrictions on the size parameter.

src/libsystemd-bus/bus-kernel.c

@@ -24,6 +24,7 @@
 #endif
 
 #include <fcntl.h>
+#include <malloc.h>
 
 #include "util.h"
 
@@ -199,7 +200,7 @@ static int bus_message_setup_kmsg(sd_bus *b, sd_bus_message *m) {
                 sz += ALIGN8(offsetof(struct kdbus_msg_item, str) + dl + 1);
         }
 
-        m->kdbus = aligned_alloc(8, sz);
+        m->kdbus = memalign(8, sz);
         if (!m->kdbus)
                 return -ENOMEM;
 
@@ -500,7 +501,7 @@ int bus_kernel_read_message(sd_bus *bus, sd_bus_message **m) {
         for (;;) {
                 void *q;
 
-                q = aligned_alloc(8, sz);
+                q = memalign(8, sz);
                 if (!q)
                         return -errno;