DOCS: Moved multiarch and build system, Incorprated Scott's changes

Change-Id: I5a57846db2d4faac1aa24db4629b612657f59afb
Signed-off-by: John DeNisco <jdenisco@cisco.com>
diff --git a/docs/gettingstarted/developers/index.rst b/docs/gettingstarted/developers/index.rst
index 76feb05..8c39069 100644
--- a/docs/gettingstarted/developers/index.rst
+++ b/docs/gettingstarted/developers/index.rst
@@ -25,8 +25,10 @@
    plugins
    vnet
    featurearcs
+   multiarch/index.rst
    bihash
    vpp_api_module
    binary_api_support
+   buildsystem/index.rst
    sample_plugin