Build: Add qcbor library fetching

Change-Id: I00e8a0b6d551d01b39ca2d563ed9a75b9c4f2b72
Signed-off-by: Kevin Peng <kevin.peng@arm.com>
diff --git a/lib/ext/CMakeLists.txt b/lib/ext/CMakeLists.txt
index eb53c97..d6da886 100644
--- a/lib/ext/CMakeLists.txt
+++ b/lib/ext/CMakeLists.txt
@@ -8,3 +8,8 @@
 if(CONFIG_TFM_ERPC_TEST_FRAMEWORK)
     add_subdirectory(erpc)
 endif()
+
+if(TEST_NS_ATTESTATION OR TEST_NS_QCBOR)
+    add_subdirectory(qcbor)
+endif()
+