[PR PATCH] Fix crackcheck Makefile to allow building on Ubuntu

[github at samba.org]

There is a new pull request by candlerb against master on the Samba Samba Github repository

https://github.com/candlerb/samba candlerb/crackcheck
https://github.com/samba-team/samba/pull/114

Fix crackcheck Makefile to allow building on Ubuntu
This patch fixes the following failure when attempting to build crackcheck under Ubuntu 16.04:

~~~
# make
gcc  -O2   -c -o crackcheck.o crackcheck.c
crackcheck.c: In function ‘main’:
crackcheck.c:91:15: warning: implicit declaration of function ‘getopt’ [-Wimplicit-function-declaratio
  while ( (c = getopt(argc, argv, "d:cs")) != EOF){
               ^
gcc  -O2 -lcrack -o crackcheck crackcheck.o
crackcheck.o: In function `main':
crackcheck.c:(.text.startup+0xee): undefined reference to `FascistCheck'
collect2: error: ld returned 1 exit status
Makefile:18: recipe for target 'crackcheck' failed
make: *** [crackcheck] Error 1
~~~

It just needs the `-lcrack` option to be moved to the end of the command line. Also adds `#include <unistd.h>` to silence the getopt warning.

A patch file from https://github.com/samba-team/samba/pull/114.patch is attached
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