entrypoint: ensure implements tool is up to date

When running things by hand it's nice to reuse the same build of
implements over and over, but for the casual contributor
who may need to run implements as part of adding a new API we want to
ensure the tool being run is up-to-date with the repo.
Cleaning the binary first is a quick and dirty way of getting there.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

entrypoint.sh

@@ -234,7 +234,7 @@ pre_all_tests() {
     # Prepare Go code
     go get -t -v ${BUILD_TAGS} ./...
     diff -u <(echo -n) <(gofmt -d -s .)
-    make implements
+    make clean-implements implements
 
     # Reset whole-module coverage file
     echo "mode: count" > "cover.out"