Add icarus verilog to gatemate docker image

gatemate.Dockerfile

@@ -5,5 +5,12 @@ RUN cd /root && \
     tar xf gatemate-toolchain.tar.gz -C /opt/ && \
     rm gatemate-toolchain.tar.gz
 
+RUN apt-get update -qq && \
+    DEBIAN_FRONTEND=noninteractive apt-get -y install --no-install-recommends \
+    iverilog && \
+    apt-get -y upgrade && apt-get autoclean && apt-get clean && apt-get -y autoremove && \
+    update-ca-certificates && \
+    rm -rf /var/lib/apt/lists/*
+
 ## Enhance path variable
 ENV PATH "/opt/cc-toolchain-linux/bin/p_r:$PATH"