This should include a fix for S_ISUID that we "lost" when switching away from mes-m2's libc. See http://git.savannah.gnu.org/cgit/mes.git/commit/?id=ce54ccc2c04b0a6ec9105522e4b8b4cc278c5106
This allows creating *.checksums files instead of checking against them when UPDATE_CHECKSUMS is set to True in bootstrap.cfg. The checksums are also copied to /usr/src so they can be accessed easily after the bootstrap completes.