IVGCVSW-2115: Updated README.md

* Added line to README.md explaining the function of the get_compute_library.sh script

Change-Id: If6be1c64443dcd6d0a08a12485de3d38614542f0
diff --git a/README.md b/README.md
index 3aa3a8c..ebe113c 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,8 @@
 
 The 'armnn/samples' directory contains SimpleSample.cpp. A very basic example of the ArmNN SDK API in use.
 
+Note that Arm NN needs to be built against a particular version of ARM's Compute Library. The get_compute_library.sh in the scripts subdirectory will clone the compute library from the review.mlplatform.org github repository into a directory alongside armnn named 'clframework' and checkouts the correct revision
+
 ### License
 
 Arm NN is provided under the [MIT](https://spdx.org/licenses/MIT.html) license.