TEST: update example.json file

Author: Qinghao Shi

tools/test/examples/examples.json

@@ -464,11 +464,11 @@
     {
         "name": "mbed-os-example-atecc608a",
         "github": "https://github.com/ARMmbed/mbed-os-example-atecc608a",
-        "mbed": [],
-        "test-repo-source": "github",
+        "sub-repo-example": true,
+        "subs": ["atecc608a"],
         "features" : [],
         "targets" : ["K64F"],
-        "toolchains" : [],
+        "toolchains" : ["GCC_ARM"],
         "exporters": [],
         "compile" : true,
         "export": true,