update dockerfiles

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

masscan/Dockerfile

@@ -8,6 +8,7 @@ RUN apt-get update && apt-get install -y \
 	&& rm -rf /var/lib/apt/lists/*
 
 RUN buildDeps=' \
+		clang \
 		gcc \
 		git \
 		make \