Hi Mark,

The bug stems from ‘ld-wrapper-boot0’ and was introduced in
d75acc293dd3e63db8739aa04c021df917aa1b80.  The problem is that
‘ld-wrapper-boot0’ uses the value of (%current-system) on the machine
that builds the derivation—i.e., hydra.gnu.org.

Instead, it should use the value of the system we’re building for, so
its evaluation should be delayed, as is the case for ‘inputs’ fields.

The result of this bug is that ‘ld-wrapper-boot0’ is bogus on all arches
except x86_64.  However, this is harmless: we don’t need this ld wrapper
anyway, except for GNU/Hurd.

So, a short-term hack might be this: