scripts: fix missing space when using CT_EXTRA_FLAGS_FOR_HOST

CT_EXTRA_FLAGS_FOR_HOST needs a preceding space to separate it from
any other options that have already been set.

Signed-off-by: Michael Hope <michael.hope@linaro.org>

# m68k specific configuration file

## depends on EXPERIMENTAL

##

## select ARCH_SUPPORTS_32

## select ARCH_DEFAULT_32

## select ARCH_DEFAULT_BE

## select ARCH_SUPPORT_CPU

##

## help The m68k architecture