I have spent some time today getting Sonic Pi to build with the latest commits (currently #8c9912). A couple of changes have affected the process.
First commit #e28790 updates the scope shared memory files to give compatability with scsynth3.9 This is the development version. If you build with this commit SP will crash as it starts (on a Mac). The solution is either to build SuperCollider for 3.9beta (or there is a built beta release for SC on this version from which you can extract scsynth, but you will have to build the extension plugins as they have a new interface), or revert the commit and continue to use scsynth 3.8 and associated plugins.
Secondly, there has been a fairly major change in the arrangement of the folders in Sonic Pi. All the ruby stuff is placed in a new ruby folder inside server. This includes the sonicpi/lib folder, the vendor folder and the bin folder. The only other folder supplied in the server folder is the erlang folder. an rb-native folder is created in the ruby folder when the extensions are built but there is no os specific folder osx,raspberry,linux now.
Similarly a native folder is created in the server folder which holds the osmid folder, a ruby folder containing bin/ruby ( a shortcut pointing to the installed ruby to use), a supercollider folder containing a plugins folder and scsynth which also has a soft link in the native folder. Again there are no OS specific folders any more.
Consequently there are some adjustments to be made, particularly if you use a build script.
The main change is that compile-extensions.rb and i18n-tool.rb are now in server/ruby/bin rather than server/bin
I have summarised this here
EDIT
I’ve now downloaded a built Supercollider3.9beta and extracted scsynth and plugins from it. I’ve also downloaded source for 3.9 and for the 3.9 extra plugins and built those. Using these new items I restored the update to the scope files and rebuilt and they all work well together.