Checking out this directory will also pull in the latest Squeak Unix VM tree:

$ svn propget svn:externals http://tinlizzie.org/olpc/sugar/squeak
platforms/Cross http://squeakvm.org/svn/squeak/trunk/platforms/Cross
platforms/unix  http://squeakvm.org/svn/squeak/trunk/platforms/unix

To build:

$ svn co http://tinlizzie.org/olpc/sugar/squeak
$ cd squeak
$ ./autogen.sh --prefix=...
$ make
$ make install