If you download only the gcc-core-4.2 snapshot, for example ftp://ftp.uvsq.fr/pub/gcc/snapshots/4.2-20060401/gcc-core-4.2-20060401.tar.bz2 and do a ../configure --enable-languages=c && make make will stop complaining about some objC file that is not in the package:
make[2]: *** No rule to make target `../../gcc/objc/objc-act.c', needed by `s-gtype'. Stop. -- Summary: Fail to build gcc-core-4.2 snapshots Product: gcc Version: 4.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: bootstrap AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: sebastian dot pop at cri dot ensmp dot fr http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27063