Only look for armcc if component_build_armcc or component_build_yotta
is to be executed, instead of requiring the option --no-armcc.
You can still pass --no-armcc, but it's no longer required when
listing components to run. With no list of components or an exclude
list on the command line, --no-armcc is equivalent to having
build_armcc in the exclude list.
Omit the yotta pre-checks if the build_yotta component is not going to
be executed. This makes --no-yotta equivalent to specifying a list of
components to run that doesn't include build_yotta.