Re-applies the target architecture and FPU changes from cc50788
(reverted on dev in a3b718c) on top of the soft-float baseline: Cortex-M7
with hardware VFPv5 FPU (-mfloat-abi=hard), plus uClibc-ng built with
UCLIBC_HAS_FPU=y. Hard-float support and the resulting device-side fixes
are being developed here rather than on dev directly.