ARM Multilibs with --with-mode=thumb

[gnubie gnubie]

Hi,
I've noticed odd behaviour when building an ARM compiler with GCC 4.7,
--with-mode=thumb and multilibs enabled.

If I do a standard c/c++ newlib build with the following multilib options:
MULTILIB_OPTIONS     += marm mthumb
MULTILIB_DIRNAMES    += arm thumb

we get the following static libs:
./arm-none-eabi/lib/libssp_nonshared.a
./arm-none-eabi/lib/libcc.a
./arm-none-eabi/lib/libc.a
./arm-none-eabi/lib/libsupc++.a
./arm-none-eabi/lib/libnosys.a
./arm-none-eabi/lib/libstdc++.a
./arm-none-eabi/lib/libm.a
./arm-none-eabi/lib/thumb/libssp_nonshared.a
./arm-none-eabi/lib/thumb/libcc.a
./arm-none-eabi/lib/thumb/libc.a
./arm-none-eabi/lib/thumb/libsupc++.a
./arm-none-eabi/lib/thumb/libnosys.a
./arm-none-eabi/lib/thumb/libstdc++.a
./arm-none-eabi/lib/thumb/libm.a
./arm-none-eabi/lib/thumb/libssp.a
./arm-none-eabi/lib/thumb/libg.a
./arm-none-eabi/lib/libssp.a
./arm-none-eabi/lib/libg.a
./lib/gcc/arm-none-eabi/4.7.3/libgcc.a
./lib/gcc/arm-none-eabi/4.7.3/libgcov.a
./lib/gcc/arm-none-eabi/4.7.3/thumb/libgcc.a
./lib/gcc/arm-none-eabi/4.7.3/thumb/libgcov.a
./lib/libarm-none-eabi-sim.a
./lib/libiberty.a

That's all great.  Now, if I enable thumb mode as the default with
--with-mode=thumb, I get the following libs:
./arm-none-eabi/lib/libcc.a
./arm-none-eabi/lib/libc.a
./arm-none-eabi/lib/libnosys.a
./arm-none-eabi/lib/libm.a
./arm-none-eabi/lib/thumb/libssp_nonshared.a
./arm-none-eabi/lib/thumb/libcc.a
./arm-none-eabi/lib/thumb/libc.a
./arm-none-eabi/lib/thumb/libsupc++.a
./arm-none-eabi/lib/thumb/libnosys.a
./arm-none-eabi/lib/thumb/libstdc++.a
./arm-none-eabi/lib/thumb/libm.a
./arm-none-eabi/lib/thumb/libssp.a
./arm-none-eabi/lib/thumb/libg.a
./arm-none-eabi/lib/libg.a
./lib/gcc/arm-none-eabi/4.7.3/libgcc.a
./lib/gcc/arm-none-eabi/4.7.3/libgcov.a
./lib/gcc/arm-none-eabi/4.7.3/thumb/libgcc.a
./lib/gcc/arm-none-eabi/4.7.3/thumb/libgcov.a
./lib/libarm-none-eabi-sim.a
./lib/libiberty.a

As you can see, we've lost a load of arm libs: libssp, libstdc++ and libsupc++.

I haven't tried 4.8 yet, but i can't see any bug reports to suggest
anything has changed.

What am I missing here?

Thanks,
Carlos