Docker build: prepare source as prerequisite

Signed-off-by: Haitao Huang <4699115+haitaohuang@users.noreply.github.com>

Author: haitaohuang

docker/build/Dockerfile

@@ -53,8 +53,6 @@ RUN apt-get update && apt-get install  -y \
 WORKDIR /linux-sgx
 COPY . .
 
-RUN ./download_prebuilt.sh
-
 RUN make sdk_install_pkg_no_mitigation
 
 WORKDIR /opt/intel

docker/build/README.md

@@ -7,6 +7,10 @@ Files in this directory demonstrate how to build and install the SGX SDK and PSW
 ###  Prerequisites
 1. Install [Docker and Compose](https://docs.docker.com/) and configure them properly following their respective installation guide.
 2. Install [SGX Flexible Launch Control driver](https://github.com/intel/SGXDataCenterAttestationPrimitives/tree/master/driver/linux). **Note**: See below to run with the Legacy Launch Control driver.
+3. In the root directory of this repo, prepare source code and download prebuilt binaries:
+```
+$ make preparation
+```
 
 ### Run with Docker Compose
 This will start AESM and an SGX sample on one terminal using docker-compose.