clang+llvm-9.0.0-x86_64-linux-gnu-ubuntu-14.04 links against libc++ instead of libstdc++

The Ubuntu 14.04 prebuilt binary on LLVM Download Page seems to be built against libc++:

% nm -Cu libLLVMCore.a | sed -n '/ std::__1/{p;q}'
                 U std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::find(char, unsigned long) const

Is this expected? With a brief reading of
https://llvm.org/docs/ReleaseProcess.html, I guess the prebuilt binaries were likely built with llvm/utils/release/test-release.sh, but I cannot find any LLVM_ENABLE_LIBCXX setting in the script.

From: llvm-dev <llvm-dev-bounces@lists.llvm.org> On Behalf Of Fangrui Song
via llvm-dev

...

The Ubuntu 14.04 prebuilt binary on
LLVM Download Page seems to be built against
libc++:

% nm -Cu libLLVMCore.a | sed -n '/ std::__1/{p;q}'
                 U std::__1::basic_string<char, std::__1::char_traits<char>,
std::__1::allocator<char> >::find(char, unsigned long) const

Is this expected? With a brief reading of
How To Validate a New Release — LLVM 18.0.0git documentation, I guess the prebuilt binaries
were likely built with llvm/utils/release/test-release.sh, but I cannot find any
LLVM_ENABLE_LIBCXX setting in the script.

Yes, I believe I added that to "-configure-flags" for Ubuntu 14. I don't specifically recall why I added it, but it's *possible* that I would've done that if the libstdc++ and/or glibc were missing necessary features for some of the llvm projects or test suite programs.

I can rebuild it without that extra configure flags and upload that in addition. I guess I'd use the same triple for now and rename the tarball with some kind of suffix to clarify.

-Brian