docker: install gawk

It's explicitly needed by the kernel, but apparently not
always pulled in.

Signed-off-by: Johannes Berg <[email protected]>

Author: jmberg

docker/Dockerfile

@@ -13,6 +13,7 @@ RUN apt-get update && apt-get install -y \
 	ccache \
 	flex \
 	bison \
+	gawk \
 	libssl-dev \
 	libelf-dev \
 	clang lld llvm \