Provide option to build the SDK

A simple solution to allow this script to build the SDK when needed

Change-Id: Ic2cbf6adff5c99eee1860f3e6e961a9b61bf042e
Signed-off-by: Andrew Geissler <andrewg@us.ibm.com>
diff --git a/build-setup.sh b/build-setup.sh
index 7930992..f092f45 100755
--- a/build-setup.sh
+++ b/build-setup.sh
@@ -7,6 +7,8 @@
 #   distro = fedora|ubuntu|ubuntu:14.04|ubuntu:16.04
 #   obmcdir = <name of openbmc src dir> (default openbmc)
 #   WORKSPACE = <location of base openbmc/openbmc repo>
+#   BITBAKE_OPTS = <optional, set to "-c populate_sdk" or whatever other
+#                   bitbake options you'd like to pass into the build>
 
 # Trace bash processing. Set -e so when a step fails, we fail the build
 set -xeo pipefail
@@ -217,7 +219,7 @@
 EOF_CONF
 
 # Kick off a build
-bitbake obmc-phosphor-image
+bitbake ${BITBAKE_OPTS} obmc-phosphor-image
 
 EOF_SCRIPT