gci: Add rust configuration to Github actions

.github/scripts/setup.sh

@@ -3,6 +3,8 @@
 export DEBIAN_FRONTEND=noninteractive
 export BITCOIN_VERSION=0.20.1
 export ELEMENTS_VERSION=0.18.1.8
+export RUST_VERSION=nightly
+
 sudo useradd -ms /bin/bash tester
 sudo apt-get update -qq
 
@@ -66,3 +68,8 @@ sudo chmod 0440 /etc/sudoers.d/tester
        elements-$ELEMENTS_VERSION-x86_64-linux-gnu.tar.bz2 \
        elements-$ELEMENTS_VERSION
 )
+
+if [ "$RUST" == "1" ]; then
+    curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- \
+      -y --default-toolchain ${RUST_VERSION}
+fi