tcmode: resolve issues with the gcc version extraction

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
tcmode: kill cross-canadian bits from TOOLCHAIN_HOST_TASK

We expect folks to use Sourcery G++ on the SDKMACHINE as well, so there's no
point building and shipping an internal toolchain for it.

Signed-off-by: Christopher Larson <chris_larson@mentor.com>
external-toolchain: improve debug messages

Signed-off-by: Christopher Larson <chris_larson@mentor.com>