global: Disable xPL phases when we have enabled COMPILE_TEST

global: Disable xPL phases when we have enabled COMPILE_TEST

Due to how we implement the logic for selecting what should/shouldn't be
built in a given phase it becomes extremely cumbersome to make these
phases link when configured by "allyesconfig". As a starting point for
being able to enable "allyesconfig" and expand our static coverage,
disable all other phases in this case.

Future work can be done to enable other phases as time and interest
permit.

Signed-off-by: Tom Rini <trini@konsulko.com>