[1.9] trunk is failing to build on OS X 10.4

Hello, since yesterday or the day before, trunk/1.9 fails to build with
the following error:

ruby -I… …/tool/compile_prelude.rb …/prelude.rb miniprelude.c
gcc-mp-4.2 -O -pipe -pipe -fno-common -I.
-I.ext/include/i686-darwin8.11.1 -I…/include -I… -DRUBY_EXPORT
-D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -o miniprelude.o -c miniprelude.c
In file included from miniprelude.c:2:
…/vm_core.h:349: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
attribute’ before ‘rb_jmpbuf_t’
…/vm_core.h:352: error: expected specifier-qualifier-list before
…/vm_core.h:456: error: expected specifier-qualifier-list before
make: *** [miniprelude.o] Error 1

(ruby is from macports at 1.9.6_p111), trunk is at revision 15885, gcc
4.2 is used, OS X 10.4.11.

URL: http://svn.ruby-lang.org/repos/ruby/trunk
Repository Root: http://svn.ruby-lang.org/repos/ruby
Repository UUID: b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Revision: 15885
Node Kind: directory
Schedule: normal
Last Changed Author: matz
Last Changed Rev: 15885
Last Changed Date: 2008-04-01 23:54:16 +0200 (Tue, 01 Apr 2008)

I suspect r15871 being the culprit.