crosutils: make cros_run_unit_tests prepare before building tests

cros_run_unit_tests

Index: cros_run_unit_tests
diff --git a/cros_run_unit_tests b/cros_run_unit_tests
index 9a17b4452df63f49df68c12b5eec9430a3419e81..169edde582b7549b3e304ca4caddd2a0b5c0804c 100755
--- a/cros_run_unit_tests
+++ b/cros_run_unit_tests
@@ -42,10 +42,10 @@ function record_test_failure() {
 
 function run_unit_test() {
   FEATURES="-buildpkg -digest noauto" \
-    ebuild-${FLAGS_board} "${1}" clean unpack configure test
+    ebuild-${FLAGS_board} "${1}" clean unpack prepare configure test
 }
 
-# Parse command line and die if unexpected paramters given.
+# Parse command line and die if unexpected parameters given.
 FLAGS_HELP="usage: ${0} [flags]"
 FLAGS "${@}" || exit 1
 eval set -- "${FLAGS_ARGV}"