Build failure using clang++/libc++

Hello,

I'm trying to build libclc using clang++ 4.0.0-rc2, which uses libc++ as
its standard library.

The build fails with the following:

In file included from utils/prepare-builtins.cpp:1:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitcodeReader.h:17:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitCodes.h:21:
In file included from /mnt/lfs/tools/include/llvm/ADT/SmallVector.h:20:
In file included from /mnt/lfs/tools/include/llvm/Support/MathExtras.h:18:
In file included from /mnt/lfs/tools/include/llvm/Support/SwapByteOrder.h:19:
In file included from /mnt/lfs/tools/include/llvm/Support/DataTypes.h:33:
/mnt/lfs/tools/bin/../include/c++/v1/cmath:315:9: error: no member named 'isfinite' in the global namespace
using ::isfinite;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:316:9: error: no member named 'isinf' in the global namespace
using ::isinf;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:317:9: error: no member named 'isnan' in the global namespace
using ::isnan;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:318:9: error: no member named 'isnormal' in the global namespace
using ::isnormal;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:319:9: error: no member named 'isgreater' in the global namespace
using ::isgreater;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:320:9: error: no member named 'isgreaterequal' in the global namespace
using ::isgreaterequal;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:321:9: error: no member named 'isless' in the global namespace
using ::isless;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:322:9: error: no member named 'islessequal' in the global namespace
using ::islessequal;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:323:9: error: no member named 'islessgreater' in the global namespace
using ::islessgreater;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:324:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
       ~~^
/mnt/lfs/tools/bin/../include/c++/v1/cmath:325:9: error: no member named 'isunordered' in the global namespace
using ::isunordered;
       ~~^
1 warning and 13 errors generated.

If I specify -stdlib=libstdc++, I get the following error:

In file included from utils/prepare-builtins.cpp:1:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitcodeReader.h:17:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitCodes.h:21:
In file included from /mnt/lfs/tools/include/llvm/ADT/SmallVector.h:20:
In file included from /mnt/lfs/tools/include/llvm/Support/MathExtras.h:18:
In file included from /mnt/lfs/tools/include/llvm/Support/SwapByteOrder.h:19:
In file included from /mnt/lfs/tools/include/llvm/Support/DataTypes.h:33:
In file included from /usr/lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/cmath:45:
In file included from /usr/include/math.h:48:
/mnt/lfs/tools/include/bits/mathdef.h:19:3: error: "Never use <bits/mathdef.h> directly; include <complex.h> instead"
# error "Never use <bits/mathdef.h> directly; include <complex.h> instead"
   ^
In file included from utils/prepare-builtins.cpp:1:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitcodeReader.h:17:
In file included from /mnt/lfs/tools/include/llvm/Bitcode/BitCodes.h:21:
In file included from /mnt/lfs/tools/include/llvm/ADT/SmallVector.h:20:
In file included from /mnt/lfs/tools/include/llvm/Support/MathExtras.h:18:
In file included from /mnt/lfs/tools/include/llvm/Support/SwapByteOrder.h:19:
In file included from /mnt/lfs/tools/include/llvm/Support/DataTypes.h:33:
/usr/lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/cmath:1101:11: error: no member named 'double_t' in the global namespace
   using ::double_t;
         ~~^
/usr/lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/cmath:1102:11: error: no member named 'float_t' in the global namespace
   using ::float_t;
         ~~^

Please advise what to do. I'd like to continue usign libc++ as my standard library.