tests: Fix warning in 05-sim-long_jumps.c

Commit 3c2da11 "tests: improve 05-sim-long_jumps to work better
across arch/ABIs" introduced the following warning.  Let's fix it.

	05-sim-long_jumps.c: In function ‘main’:
	05-sim-long_jumps.c:68:25: warning: implicit declaration of function ‘free’ [-Wimplicit-function-declaration]
	   68 |                         free(syscall);

Acked-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

tests/05-sim-long_jumps.c

@@ -23,6 +23,7 @@
 #include <errno.h>
 #include <unistd.h>
 #include <limits.h>
+#include <stdlib.h>
 
 #include <seccomp.h>