Update Quickstart.rst to fix build information (#540)

docs/source/Quickstart.rst

@@ -16,28 +16,29 @@ Building RRFS workflow
 
       .. code-block:: console
 
-         git clone https://github.com/NOAA-EMC/rrfs-workflow.git
+        git clone https://github.com/NOAA-EMC/rrfs-workflow.git
 
-   #. Check out the external components:
+   #. Move to the sorc directory:
 
       .. code-block:: console
 
-         cd rrfs-workflow/sorc
-         ./manage_externals/checkout_externals
+        cd rrfs-workflow/sorc
 
-   #. Set up the build environment and build the executables:
+   #. Build the needed executables for the workflow: 
 
       .. code-block:: console
-            
-         ./app_build.sh
 
-      Alternatively, the above command can be followed by the platform (machine) name as follows:
+        ./app_build.sh --extrn --noifi --nogtg
+      The above command uses the ``--extrn`` flag to do the code checkout, the ``--noifi`` flag avoids   building the IFI (icing) library, and the ``--nogtg`` flag avoids building the GTG (turbulence) library.  Most users do not have access to the IFI and GTG codes.
+
+   #. The above command is equal to:
 
       .. code-block:: console
             
-         ./app_build.sh --platform=<machine>
+         ./manage_externals/checkout_externals
+         ./app_build.sh -p=[machine] --noifi --nogtg
 
-      where ``<machine>`` is ``wcoss2``, ``hera``, ``jet``, ``orion``, or ``hercules``.
+      where ``<machine>`` is one of ``wcoss2``, ``hera``, ``jet``, ``orion``, or ``hercules``  
 
    #. Move to the home directory (rrfs-workflow):