Cannot build libc++ with Clang?

I have a script to build LLVM, Compiler Front End (Clang), Compiler RT
and Extras. It has worked fine since the Clang 3.2 days or so.

After building and installing Clang 3.5, Clang is having trouble
finding headers and runtime libraries on OS X 10.9. Attempts to
compile/link fails when using a minimal command line. If I add headers
with -I, then links fail. So I have to add libraries with -L and -l.

So I'm trying to build libc++ in-tree. I downloaded
libcxx-3.5.0.src.tar.xz, unpacked to libcxx. It was then moved to
llvm/projects. The same was done for to libcxxabi-3.5.0.src.tar.xz. It
was unpacked to libcxxabi and moved to llvm/projects. The instructions
were provided at

I then configure as normal with:

    # Determine if Apple
    IS_DARWIN=`uname -s | egrep -i -c "Darwin"`
    if [ $IS_DARWIN -ne 0 ]; then
      OTHER_OPTIONS=" --enable-libcpp"

    echo "Configuring build"
    mkdir -p build
    cd build
    ../llvm/configure --enable-optimized --enable-cxx11 $OTHER_OPTIONS

Finally, I build:

    # 'make cxx' for libc++ is from
    echo "Running make"
    make cxx
    make -j2

Unfortunately, no libc++.{a|so|dylib|etc}.

--enable-libcpp was needed to compile the LLVM gear for OS X 10.7 and
10.8. But removing it does not help on OS X 10.9 (I was taking a stab
in the dark).

What am I doing wrong?

Thanks in advance.