move docker files

contrib/docker/alpine-arm32v7/Dockerfile

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+# install from an image
+# download first an appropriate tar.gz image into the current directory
+# from: <https://github.com/alpinelinux/docker-alpine/tree/edge/armv7>
+FROM scratch
+
+# Substitute the image name that was downloaded
+ADD alpine-minirootfs-20240329-armv7.tar.gz /
+
+# Install tools
+RUN apk add build-base make cmake
+RUN apk add git
+RUN apk add vim
+
+RUN mkdir -p  /home/dev
+WORKDIR /home/dev
+
+# Get mimalloc
+RUN git clone https://github.com/microsoft/mimalloc -b dev2
+RUN mkdir -p mimalloc/out/release
+RUN mkdir -p mimalloc/out/debug
+
+# Build mimalloc debug
+WORKDIR /home/dev/mimalloc/out/debug
+RUN cmake ../.. -DMI_DEBUG_FULL=ON
+RUN make -j
+RUN make test
+
+CMD ["/bin/sh"]