Mount CARGO_HOME into build container

docker-build.sh

@@ -5,6 +5,7 @@ cd "$(dirname "$0")"
 
 package="$1"
 builder_image="mullvad-slint-musl-builder"
+cargo_home="${CARGO_HOME:-$HOME/.cargo}"
 . "$HOME/.abuild/abuild.conf"
 
 docker build . -f Dockerfile -t "$builder_image"
@@ -14,8 +15,10 @@ docker run --rm \
     -v "$PACKAGER_PRIVKEY":/key.rsa:ro \
     -v "$PACKAGER_PRIVKEY.pub":/key.rsa.pub:ro \
     -v "$PACKAGER_PRIVKEY.pub":/etc/apk/keys/key.rsa.pub:ro \
-    -v ./target:/cargo-target \
     -v ./packages:/root/packages \
+    -v "$cargo_home":/cargo-home \
+    -e "CARGO_HOME=/cargo-home" \
+    -v ./target:/cargo-target \
     -e "CARGO_TARGET_DIR=/cargo-target" \
     -it \
     "$builder_image" \