Added docker build scripts for alpine and ubuntu

docker-build/Dockerfile-alpine

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+ARG VERSION=latest
+FROM alpine:${VERSION} AS build
+
+# add c build tools
+RUN apk add build-base
+
+# add git
+RUN apk add git
+
+# add php dev
+RUN apk add php7-dev
+
+# add zlib dev
+RUN apk add zlib-dev
+
+# clone php-spx
+RUN git clone https://github.com/NoiseByNorthwest/php-spx.git
+
+# set workdir
+WORKDIR /php-spx
+
+# checkout release
+RUN git checkout tags/v0.4.10
+
+# build php-spx
+RUN phpize
+RUN ./configure
+RUN make
+
+# start again with a new image
+FROM scratch
+
+# get version
+ARG VERSION
+
+# copy spx module from alpine image to the scratch image so files can be copied back to host
+COPY --from=build /php-spx/modules/spx.so alpine-$VERSION/spx.so

docker-build/Dockerfile-ubuntu

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+ARG VERSION=latest
+FROM ubuntu:${VERSION} AS build
+
+# https://dev.to/setevoy/docker-configure-tzdata-and-timezone-during-build-20bk
+ENV TZ=Europe/Berlin
+RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
+
+# update system
+RUN apt update
+RUN apt upgrade -y
+
+# install git
+RUN apt install -y git
+
+# install php development tools
+RUN apt install -y php-dev
+
+# install zlib development tools
+RUN apt install -y zlib1g-dev
+
+# clone php-spx
+RUN git clone https://github.com/NoiseByNorthwest/php-spx.git
+
+# set workdir
+WORKDIR /php-spx
+
+# checkout release
+RUN git checkout tags/v0.4.10
+
+# build php-spx
+RUN phpize
+RUN ./configure
+RUN make
+
+# start again with a new image
+FROM scratch
+
+# get version
+ARG VERSION
+
+# copy spx module from ubuntu image to the scratch image so files can be copied back to host
+COPY --from=build /php-spx/modules/spx.so ubuntu-$VERSION/spx.so

docker-build/build.sh

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+# build for ubuntu 20.04
+DOCKER_BUILDKIT=1 docker build --file Dockerfile-ubuntu --build-arg "VERSION=20.04" --output type=local,dest=lib .
+
+# build for ubuntu 18.04
+DOCKER_BUILDKIT=1 docker build --file Dockerfile-ubuntu --build-arg "VERSION=18.04" --output type=local,dest=lib .
+
+# build for alpine 3.14.0
+DOCKER_BUILDKIT=1 docker build --file Dockerfile-alpine --build-arg "VERSION=3.14.0" --output type=local,dest=lib .