glibc: do not enable memory tagging on aarch64 just yet

Sadly, it seems to break copy-on-write as reported here:
https://lists.openembedded.org/g/openembedded-core/message/153082



(From OE-Core rev: 6891217346128cf529c15192defa096378fc5091)

Signed-off-by: Alexander Kanavin <alex.kanavin@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>