update entrypoint.sh to take care of possible network\installation is…

…sues and timeouts

Add precondition detection:
The installation of reviewdog in the container will fail if there is a network timeout. Therefore, if reviewdog does not exist, exit directly to avoid finding the problem after downloading checkstyle, which is a waste of time.

Downloading checkstyle theory also takes time. Before time-consuming operation (non-real-time response), output log feedback current process.
# Conflicts:
#	entrypoint.sh

entrypoint.sh

@@ -2,6 +2,8 @@
 
 echo "Running check"
 
+command -v reviewdog >/dev/null 2>&1 || { echo >&2 "reviewdog: not found"; exit 1; }
+
 set -e
 
 if [ -n "${GITHUB_WORKSPACE}" ] ; then
@@ -18,6 +20,7 @@ printenv
 ls
 
 # fetch checkstyle of a requested version
+echo "Downloading Checkstyle v${INPUT_CHECKSTYLE_VERSION}"
 wget -O - -q "https://github.com/checkstyle/checkstyle/releases/download/checkstyle-${INPUT_CHECKSTYLE_VERSION}/checkstyle-${INPUT_CHECKSTYLE_VERSION}-all.jar" > /checkstyle.jar
 
 exec java -jar /checkstyle.jar "${INPUT_WORKDIR}" -c "${INPUT_CHECKSTYLE_CONFIG}" "${INPUT_WORKDIR}" ${OPT_PROPERTIES_FILE} -f xml \