Update Dockerfile to work on latest version of Docker (#6087)

* Update Dockerfile to use the non legacy syntax `ENV key=value` instead of `ENV key value`

Dockerfile

@@ -4,8 +4,8 @@ COPY . lighthouse
 ARG FEATURES
 ARG PROFILE=release
 ARG CARGO_USE_GIT_CLI=true
-ENV FEATURES $FEATURES
-ENV PROFILE $PROFILE
+ENV FEATURES=$FEATURES
+ENV PROFILE=$PROFILE
 ENV CARGO_NET_GIT_FETCH_WITH_CLI=$CARGO_USE_GIT_CLI
 RUN cd lighthouse && make
 

lcli/Dockerfile

@@ -5,7 +5,7 @@ FROM rust:1.75.0-bullseye AS builder
 RUN apt-get update && apt-get -y upgrade && apt-get install -y cmake libclang-dev
 COPY . lighthouse
 ARG FEATURES
-ENV FEATURES $FEATURES
+ENV FEATURES=$FEATURES
 RUN cd lighthouse && make install-lcli
 
 FROM ubuntu:22.04