BR2_PACKAGE_HOST_RUSTC_TARGET_ARCH_SUPPORTS is not enabled when ARMv8
target hardware is combined with 32-bit software. That is because ARMv7
(32-bit) toolchain is only enabled for BR2_ARM_CPU_ARMV7A which is
mutually exclusive with BR2_ARM_CPU_ARMV8A.
Use ARMv7 toolchain for 32-bit software.
Cc: James Hilliard <james.hilliard1@gmail.com>
Reported-by: Oscar Gomez Fuente <oscargomezf@gmail.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>