[SPARK-22777][SCHEDULER] Kubernetes mode dockerfile permission and distribution

# What changes were proposed in this pull request?
1. entrypoint.sh for Kubernetes spark-base image is marked as executable (644 -> 755)
2. make-distribution script will now create kubernetes/dockerfiles directory when Kubernetes support is compiled.

## How was this patch tested?
Manual testing

cc/ ueshin jiangxb1987 mridulm vanzin rxin liyinan926

Author: foxish <[email protected]>

Closes #20007 from foxish/fix-dockerfiles.

Author: foxish

dev/make-distribution.sh

@@ -168,12 +168,18 @@ echo "Build flags: $@" >> "$DISTDIR/RELEASE"
 # Copy jars
 cp "$SPARK_HOME"/assembly/target/scala*/jars/* "$DISTDIR/jars/"
 
-# Only create the yarn directory if the yarn artifacts were build.
+# Only create the yarn directory if the yarn artifacts were built.
 if [ -f "$SPARK_HOME"/common/network-yarn/target/scala*/spark-*-yarn-shuffle.jar ]; then
   mkdir "$DISTDIR/yarn"
   cp "$SPARK_HOME"/common/network-yarn/target/scala*/spark-*-yarn-shuffle.jar "$DISTDIR/yarn"
 fi
 
+# Only create and copy the dockerfiles directory if the kubernetes artifacts were built.
+if [ -d "$SPARK_HOME"/resource-managers/kubernetes/core/target/ ]; then
+  mkdir -p "$DISTDIR/kubernetes/"
+  cp -a "$SPARK_HOME"/resource-managers/kubernetes/docker/src/main/dockerfiles "$DISTDIR/kubernetes/"
+fi
+
 # Copy examples and dependencies
 mkdir -p "$DISTDIR/examples/jars"
 cp "$SPARK_HOME"/examples/target/scala*/jars/* "$DISTDIR/examples/jars"