新增learn-kubernetes（https://github.com/yyong-brs/learn-kubernetes）相关文件

learn/learn-kubernetes-master/kiamol/ch17/docker-images/rbac-tools/Dockerfile

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+ARG ALPINE_VERSION="3.15"    
+FROM alpine:$ALPINE_VERSION
+
+RUN apk add --no-cache curl git jq
+RUN apk add --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing kubectl
+
+RUN set -x; cd "$(mktemp -d)" && \
+    OS="$(uname | tr '[:upper:]' '[:lower:]')" && \
+    ARCH="$(uname -m | sed -e 's/x86_64/amd64/' -e 's/\(arm\)\(64\)\?.*/\1\2/' -e 's/aarch64$/arm64/')" && \
+    KREW="krew-${OS}_${ARCH}" && \
+    curl -fsSLO "https://github.com/kubernetes-sigs/krew/releases/latest/download/${KREW}.tar.gz" && \
+    tar zxvf "${KREW}.tar.gz" && \
+    ./"${KREW}" install krew
+
+ENV PATH="${PATH}:/root/.krew/bin"
+
+CMD exec /bin/sh -c "trap : TERM INT; (while true; do sleep 1000; done) & wait"