In SConstruct the set of executables in the devenv variable should be adjusted to use the cross compile toolchain (as opposed to host's executables).
Achieved by setting target option to the toolchain prefix which corrects compilation on macOS.

Note, TARGET_CROSS has to have the hyphen stripped as SConstruct uses the target variable with an implied hyphen (env['target'] + '-' + toolname)

Signed-off-by: David Thornley <david.thornley@touchstargroup.com>