dev-libs/beecrypt: disable assembly for x32, bug #461960

dev-libs/beecrypt: disable assembly for x32, bug #461960

beecrypt has target-specifix assembly code for arithmetics
in gas/mpopt.x86_64.m4. That assumes that x86_64 has 64-bit
items to represent bignums.

Unfortunately that is not true for x32 ABI as detection is
based on size of 'unsigned long':

```
  AC_DEFUN([BEE_CPU_BITS],[
    AC_CHECK_SIZEOF([unsigned long])
    if test $ac_cv_sizeof_unsigned_long -eq 8; then
      AC_SUBST(MP_WBITS,64U)
```

To workaround this deficiency disable assembly code completely:
pass --enable-debug.

Closes: https://bugs.gentoo.org/461960
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>
Package-Manager: Portage-2.3.51, Repoman-2.3.11