gcc trunk target libraries do not build on Darwin 12.1

[Nenad Vukicevic]

I am having trouble building the trunk om Mac OS X 10.8.1 (Darwin 12.1.0).
Configuring target libraries fails with the following error (e.g. 
libatomic):

configure:3477: checking for C compiler default output file name
configure:3499: /eng/upc/dev/nenad/gcc-trunk/bld/./gcc/xgcc 
-B/eng/upc/dev/nenad/gcc-trunk/bld/./gcc/ 
-B/usr/local/x86_64-apple-darwin12.1.0/bin/ 
-B/usr/local/x86_64-apple-darwin12.1.0/lib/ -isystem 
/usr/local/x86_64-apple-darwin12.1.0/include -isystem 
/usr/local/x86_64-apple-darwin12.1.0/sys-include    -g -O2   conftest.c >&5
Undefined symbols for architecture x86_64:
   "start", referenced from:
      -u command line option
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status

The above uses the following link lines:

/eng/upc/dev/nenad/gcc-trunk/bld/./gcc/collect2 -dynamic -arch x86_64 
-macosx_version_min 10.8.1 -weak_reference_mismatches non-weak -o a.out 
-L/eng/upc/dev/nenad/gcc-trunk/bld/./gcc 
/var/folders/z7/83zx0wdj4cx644rg7p7kgwb80000gn/T//cc6kpstu.o 
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v -idsym -dsym
collect2 version 4.8.0 20120828 (experimental)
/eng/upc/dev/nenad/gcc-trunk/bld/./gcc/collect-ld -dynamic -arch x86_64 
-macosx_version_min 10.8.1 -weak_reference_mismatches non-weak -o a.out 
-L/eng/upc/dev/nenad/gcc-trunk/bld/./gcc 
/var/folders/z7/83zx0wdj4cx644rg7p7kgwb80000gn/T//cc6kpstu.o 
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v

Test links if I add "-lcrt1.o" on the command line. I have the latest 
Xcode loaded and my Mac is up to date.

Any idea?

Nenad