[ROCm] [CI] Fix environment issue (#2708)

Signed-off-by: tjtanaa <tunjian.tan@embeddedllm.com>

docker/Dockerfile.rocm

@@ -18,8 +18,10 @@ ARG COMMON_WORKDIR=/app
 WORKDIR ${COMMON_WORKDIR}
 
 # Step 1: Setup - Install system dependencies
+# Need to include ffmpeg because vllm rocm upstream docker image
+# does not include it.
 RUN apt-get update && \
-    apt-get install -y espeak-ng git sox libsox-fmt-all jq && \
+    apt-get install -y espeak-ng ffmpeg git sox libsox-fmt-all jq && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*