Updates for cross build using docker (#1807)

Modify some sentences
Add method about cross build using docker with ACL build
Remove method for cross build using docker without ACL build
(We don't use method without ACL build anymore)

diff --git a/docs/howto/HowToUseDockerImage.md b/docs/howto/HowToUseDockerImage.md
index 08cfe02..86783ce 100644 (file)
--- a/docs/howto/HowToUseDockerImage.md
+++ b/docs/howto/HowToUseDockerImage.md
@@ -103,7 +103,7 @@ $ docker tag docker.sec.samsung.net:5000/star/nnfw/nnfw_docker_tizen:1.2 nnfw_do
 ```
 
 ## Use docker image to build `nnfw`
-There are two ways to build `nnfw` using docker image.
+Three different targets for `nnfw` can be built using docker image.
 
 1. Build `nnfw` for `x86_64` target
 ```
@@ -118,9 +118,12 @@ $ ./run docker_run_test.sh
 You can find built artifacts at `nnfw/Product/x86_64-linux.debug`.
 
 2. Cross build `nnfw` for ARM on x86_64 host
+
+You should prepare RootFS, following [Cross Building for ARM](https://github.sec.samsung.net/STAR/nnfw/blob/master/docs/howto/CrossBuildForArm.md) except ACL build and cross build steps. Then execute below commands. If your RootFS directory is different with below directory, change it to correct path and ensure the path is absolute.
 ```
 $ cd nnfw
-$ ./run docker_build_cross_arm_ubuntu_without_aclbuild.sh
+$ ROOTFS_DIR=$(pwd)/tools/cross/rootfs/arm \
+./run docker_build_cross_arm_ubuntu.sh
 ```
 You can find built artifacts at `nnfw/Product/armv7l-linux.debug/`.