new_variant: clean EC before testing

Stale output files in the EC build directory can cause intermittent
build failures. Clean the EC build before starting the new variant.

TEST=`testdata/ waddledee &&
testdata/ waddledoo && echo PASS`
After building new variants of both reference boards, you'll see
a "PASS" as the last line of output.

Change-Id: I602db6e6dc629a7e19687a6367e6cc2976c194e5
Tested-by: Paul Fagerburg <>
Auto-Submit: Paul Fagerburg <>
Reviewed-by: Karthikeyan Ramasubramanian <>
Reviewed-by: Jack Rosenthal <>
Commit-Queue: Paul Fagerburg <>
Commit-Queue: Jack Rosenthal <>
1 file changed