ci: add native aarch64-gnu docker builder

src/ci/docker/host-aarch64/aarch64-gnu/Dockerfile

@@ -0,0 +1,26 @@
+FROM ubuntu:20.04
+
+RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
+  g++ \
+  make \
+  file \
+  curl \
+  ca-certificates \
+  python3 \
+  git \
+  cmake \
+  sudo \
+  gdb \
+  libssl-dev \
+  pkg-config \
+  xz-utils
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+ENV RUST_CONFIGURE_ARGS \
+ --build=aarch64-unknown-linux-gnu \
+ --enable-sanitizers \
+ --enable-profiler \
+ --enable-compiler-docs
+ENV SCRIPT python3 ../x.py test

src/ci/docker/scripts/sccache.sh

@@ -1,6 +1,16 @@
 set -ex
 
-curl -fo /usr/local/bin/sccache \
-  https://ci-mirrors.rust-lang.org/rustc/2018-04-02-sccache-x86_64-unknown-linux-musl
+case "$(uname -m)" in
+    x86_64)
+        url="https://ci-mirrors.rust-lang.org/rustc/2018-04-02-sccache-x86_64-unknown-linux-musl"
+        ;;
+    aarch64)
+        url="https://ci-mirrors.rust-lang.org/rustc/2019-12-17-sccache-aarch64-unknown-linux-gnu"
+        ;;
+    *)
+        echo "unsupported architecture: $(uname -m)"
+        exit 1
+esac
 
+curl -fo /usr/local/bin/sccache "${url}"
 chmod +x /usr/local/bin/sccache