Comparing the log of successful and failed builds I have found
that the failed one contains -mdynamic-no-pic which does not
appear in the previous build. According Apple's doc this
should be used in "application", but it should not appear
when building libraries (at least it is my understanding).
I suspect the origin of the problem comes from
2007-05-16 Paolo Bonzini <bonzini@gnu.org>
* Makefile.def (bootstrap_stage): Replace stage_make_flags with
stage_cflags.
* Makefile.tpl (POSTSTAGE1_HOST_EXPORTS, POSTSTAGE1_FLAGS_TO_PASS):
Remove CFLAGS/LIBCFLAGS.
(configure-stage[+id+]-[+prefix+][+module+],
all-stage[+id+]-[+prefix+][+module+]): Pass it from [+stage_cflags+].
* Makefile.in: Regenerate.
but there are too many changes to allow me to go further.