MacOS: test crashes with SegFault

[mouse07410]

MacOS 10.15.6, Xcode-11.6. Current master.

$ ./testnoham 
Running tests...
  test_ntruprime_inv_int   ✓
  test_ntruprime_inv_poly  ✓
Segmentation fault: 11

$ lldb ./testnoham
(lldb) target create "./testnoham"
Current executable set to '/Users/ur20980/src/libntru/testnoham' (x86_64).
(lldb) run
error: process exited with status -1 (Error 1)
(lldb) bt
error: invalid thread
(lldb) list
   13  	int main(int argc, char** argv) {
   14  	    printf("Running tests...\n");
   15  	    ntru_set_optimized_impl();   /* normally called by the functions in ntru.h */
   16  	    uint8_t pass = test_poly();
   17  	    pass &= test_ntruprime();
   18  	    pass &= test_ntru();
   19  	    pass &= test_idxgen();
   20  	    pass &= test_bitstring();
   21  	    pass &= test_key();
   22  	    pass &= test_hash();
(lldb) ^D
$