add clang to the s390x DockerFile

Author: folkertdev

ci/docker/s390x-unknown-linux-gnu/Dockerfile

@@ -6,8 +6,9 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
         gcc-s390x-linux-gnu libc6-dev-s390x-cross \
         qemu-user \
         make \
+        clang \
         file
 
 ENV CARGO_TARGET_S390X_UNKNOWN_LINUX_GNU_LINKER=s390x-linux-gnu-gcc \
     CARGO_TARGET_S390X_UNKNOWN_LINUX_GNU_RUNNER="qemu-s390x -L /usr/s390x-linux-gnu" \
-    OBJDUMP=s390x-linux-gnu-objdump
+    OBJDUMP=s390x-linux-gnu-objdump