Adding script to fetch externals

Change-Id: Idff8255b9e414be6a037b7aad42c3496b91a9301
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..280e625
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/core_software