build.sh is a script that downloads the latest version of Clojure core as of the day you run it.
It then "backs up" to a particular version that has been tested for the process described below to complete successfully. See early in the file build.sh for the SHA1 hash and date of that version.
After backing up, build.sh applies patches that attempt to address some tickets filed against Clojure. See the file patches/patch-order.txt for the current list. A few patches address more than one ticket, and a few tickets are addressed by more than one patch. All patches are from the Clojure Jira bug tracker at:
http://dev.clojure.org/jira/browse/CLJ
In some cases small modifications have been made to the patches there, so the combination of patches will apply cleanly.