To bring up Debian 11 use Swift compiler from ubuntu 20.04

Author: shahmishal

swift-ci/master/debian/11/Dockerfile

@@ -32,6 +32,52 @@ RUN apt-get -y update && apt-get -y install \
   unzip                 \
   uuid-dev
 
+ARG SWIFT_PLATFORM=ubuntu20.04
+ARG SWIFT_VERSION=5.8.1
+ARG SWIFT_BRANCH=swift-${SWIFT_VERSION}-release
+ARG SWIFT_TAG=swift-${SWIFT_VERSION}-RELEASE
+ARG SWIFT_WEBROOT=https://download.swift.org
+ARG SWIFT_PREFIX=/opt/swift/${SWIFT_VERSION}
+
+ENV SWIFT_PLATFORM=$SWIFT_PLATFORM \
+    SWIFT_VERSION=$SWIFT_VERSION \
+    SWIFT_BRANCH=$SWIFT_BRANCH \
+    SWIFT_TAG=$SWIFT_TAG \
+    SWIFT_WEBROOT=$SWIFT_WEBROOT \
+    SWIFT_PREFIX=$SWIFT_PREFIX
+
+RUN set -e; \
+    ARCH_NAME="$(dpkg --print-architecture)"; \
+    url=; \
+    case "${ARCH_NAME##*-}" in \
+        'amd64') \
+            OS_ARCH_SUFFIX=''; \
+            ;; \
+        'arm64') \
+            OS_ARCH_SUFFIX='-aarch64'; \
+            ;; \
+        *) echo >&2 "error: unsupported architecture: '$ARCH_NAME'"; exit 1 ;; \
+    esac; \
+    SWIFT_WEBDIR="$SWIFT_WEBROOT/$SWIFT_BRANCH/$(echo $SWIFT_PLATFORM | tr -d .)$OS_ARCH_SUFFIX" \
+    && SWIFT_BIN_URL="$SWIFT_WEBDIR/$SWIFT_TAG/$SWIFT_TAG-$SWIFT_PLATFORM$OS_ARCH_SUFFIX.tar.gz" \
+    && SWIFT_SIG_URL="$SWIFT_BIN_URL.sig" \
+    # - Grab curl here so we cache better up above
+    && export DEBIAN_FRONTEND=noninteractive \
+    && apt-get -q update && apt-get -q install -y curl && rm -rf /var/lib/apt/lists/* \
+    # - Download the GPG keys, Swift toolchain, and toolchain signature, and verify.
+    && export GNUPGHOME="$(mktemp -d)" \
+    && curl -fsSL "$SWIFT_BIN_URL" -o swift.tar.gz "$SWIFT_SIG_URL" -o swift.tar.gz.sig \
+    && curl -fSsL https://swift.org/keys/all-keys.asc | gpg --import -  \
+    && gpg --batch --verify swift.tar.gz.sig swift.tar.gz \
+    # - Unpack the toolchain, set libs permissions, and clean up.
+    && mkdir -p $SWIFT_PREFIX \
+    && tar -xzf swift.tar.gz --directory $SWIFT_PREFIX --strip-components=1 \
+    && chmod -R o+r $SWIFT_PREFIX/usr/lib/swift \
+    && rm -rf "$GNUPGHOME" swift.tar.gz.sig swift.tar.gz \
+    && apt-get purge --auto-remove -y curl
+
+ENV PATH="${SWIFT_PREFIX}/usr/bin:${PATH}"
+
 USER build-user
 
 WORKDIR /home/build-user