add clarifications for build instructions

Author: guillaumeriousat

README.md

@@ -7,3 +7,25 @@ Exposes a `OrbbecPointCloud` node which can list network devices, connect to one
 ## Current status
 
 Works on linux and windows, currently tested with orbbec femto mega.
+
+## Building
+Note : if you want the OrbbecPointCloud object to work from the editor, you will need to build the debug version.
+
+### linux
+```
+git submodule --recursive --init
+./build.sh # BUILD_RELEASE=1 ./build.sh for release build
+```
+
+Note: if you have already built a release version, you will have to delete your the build folder to do a debug build.
+
+### windows
+```
+git submodule --recursive --init
+```
+
+and then, in an admin cmd/powershell prompt
+```
+:: set BUILD_RELEASE=1 :: if you want to build release
+build_windows.cmd
+```