docker: Add build-overrides for custom external rocksdb.

Signed-off-by: Jason Volk <jason@zemos.net>

docker/Dockerfile.ingredients

@@ -27,7 +27,7 @@ ARG CARGO_TERM_VERBOSE=0
 ARG RUST_BACKTRACE
 ARG JEMALLOC_OVERRIDE
 #ARG ZSTD_SYS_USE_PKG_CONFIG=0
-#ARG ROCKSDB_LIB_DIR
+ARG ROCKSDB_LIB_DIR
 
 WORKDIR /
 COPY --link --from=input . .
@@ -39,7 +39,7 @@ ENV CARGO_TERM_VERBOSE="${CARGO_TERM_VERBOSE}"
 ENV RUST_BACKTRACE="${RUST_BACKTRACE}"
 ENV JEMALLOC_OVERRIDE="${JEMALLOC_OVERRIDE}"
 #ENV ZSTD_SYS_USE_PKG_CONFIG="${ZSTD_SYS_USE_PKG_CONFIG}"
-#ENV ROCKSDB_LIB_DIR="${ROCKSDB_LIB_DIR}"
+ENV ROCKSDB_LIB_DIR="${ROCKSDB_LIB_DIR}"
 RUN \
 --mount=type=cache,dst=${RUSTUP_HOME},sharing=locked \
 --mount=type=cache,dst=${CARGO_HOME},sharing=locked \