Please check the official LLVM page for the latest instructions to install clang++.
wget https://apt.llvm.org/llvm.sh
chmod +x llvm.sh
sudo ./llvm.sh all
$ sudo apt install -y libc++-10-dev
$ cd /usr/lib/x86_64-linux-gnu
$ sudo ln -s libc++abi.so.1 libc++abi.so
$ make
$ ./test; echo $?
1 # This value comes from the enum defined in libwebrtc.