arm-none-eabi target triplet defaults to Little Endian, and so far any
submitted machine code snippets have been verified to be Little Endian.
However a user might override [ARM_]CROSS_COMPILE with an armeb toolchain,
potentially resulting in invalid machine code.
Let's be safe and enforce Little Endian mode for assembler and compiler.
Signed-off-by: Andreas Färber <firstname.lastname@example.org>
Reviewed-by: Andreas Fritiofson <email@example.com>