Add cmake to s390x docker image

CMake is used by the wasm-c-api crate's build.rs.

Signed-off-by: Matt Leon <mattleon@google.com>

Author: leonm1

bazel/external/Dockerfile.bazel

@@ -153,6 +153,7 @@ ARG DEPS_RUNTIME="\
         python3 \
         python3-dev \
         unzip \
+        cmake \
         zip"
 ARG TARGETARCH
 RUN apt-get update && \