jammy-amd64-tf-a-build: Support Nightly Rust

Also install the Rust nightly toolchain to allow testing of unstable
features like BTI and PAC.

Change-Id: Ic5d368806821e94dc3dc9d36de9be31974fd73da
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Tomás González <tomasagustin.gonzalezorlando@arm.com>
diff --git a/jammy-amd64-tf-a-build/Dockerfile b/jammy-amd64-tf-a-build/Dockerfile
index 1a4be8a..8ff7e92 100644
--- a/jammy-amd64-tf-a-build/Dockerfile
+++ b/jammy-amd64-tf-a-build/Dockerfile
@@ -110,7 +110,8 @@
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | \
-        sh -s -- --default-toolchain 1.88.0 -y
+        sh -s -- --default-toolchain 1.88.0 -y && \
+        rustup install nightly
 RUN set -ex ;\
     cargo install --locked 'tokei@12.1.*' ;\
     cargo install --locked cargo-binutils ;\