libapparmor: add missing include for socklen_t

While `include/sys/apparmor.h` makes use of `socklen_t`, it doesn't
include the `<sys/socket.h>` header to make its declaration available.
While this works on systems using glibc via transitive includes, it
breaks compilation on musl libc.

Fix the issue by including the header.

Signed-off-by: Patrick Steinhardt <ps@pks.im>

libraries/libapparmor/include/sys/apparmor.h

@@ -21,6 +21,7 @@
 #include <stdbool.h>
 #include <stdint.h>
 #include <unistd.h>
+#include <sys/socket.h>
 #include <sys/types.h>
 
 #ifdef __cplusplus