BuildSystem: Fix build on FreeBSD due to missing crypt.h

FreeBSD does not include a crypt.h include file. Definitions for
crypt() and crypt_r() are in unistd.h

ASTERISK-27042 #close

Change-Id: Ib307ee5e384870c6af50efa89fb73722dd0c3a7e

main/crypt.c

@@ -29,7 +29,7 @@
 #include "asterisk.h"
 
 #include <unistd.h>
-#if defined(HAVE_CRYPT_R)
+#if defined(HAVE_CRYPT_R) && !defined(__FreeBSD__)
 #include <crypt.h>
 #endif