Use -DINSTALL_PROPRIETARY:BOOL=ON when calling develop.py from build.sh

Required because indra/cmake/Variables.cmake uses indra/Server.cmake as a flag to indicate this is an internal build, and set INSTALL_PROPRIETARY to download and install pre-built LLKDU, FMOD and Quicktime.

We need a better way of doing that, but this should get things going for now.

build.sh

@@ -61,6 +61,7 @@ pre_build()
    configure \
     -DVIEWER_CHANNEL:STRING="$viewer_channel" \
     -DVIEWER_LOGIN_CHANNEL:STRING="$login_channel" \
+    -DINSTALL_PROPRIETARY:BOOL=ON \
     -DLOCALIZESETUP:BOOL=ON \
     -DPACKAGE:BOOL=ON
   end_section "Pre$variant"