perl: Disable builtin memcpy & string inlines with gcc/x86-64-v3

perl: Disable builtin memcpy & string inlines with gcc/x86-64-v3

PERL built with GCC 15 and -march=x86-64-v3 fails several
op/pack.t cases due to aggressive lowering of __builtin_memcpy
and inlined/fortified string ops. In pp_pack, some in-place copies
can overlap, treating memcpy as non-overlapping yields corrupted
bytes (zeros or wrong prefixes).

The issue does not reproduce with -march=core2.

When using x86-64-v3 memcpy gets emitted very aggressively
(vectorized / reordered) and assumes no overlap.

The flags force calls through libc (overlap-safe behavior),
restoring deterministic pack/unpack and fixing the test failures.

Inline functions could be faster in execution but correctness is
more important

Fixes [YOCTO #15950]

Signed-off-by: Khem Raj <raj.khem@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>