[ASan] Add aligned_alloc declaration to aligned_alloc-alignment.cc test.
aligned_alloc is not always defined in headers.
#include <stdio.h>
#include <stdlib.h>
+extern void *aligned_alloc (size_t alignment, size_t size);
+
int main() {
void *p = aligned_alloc(17, 100);
// CHECK: ERROR: AddressSanitizer: invalid allocation alignment: 17
