Docker build fails

Hey, first of all thank you for the amazing software that you are providing. I was able to compile everything up to bc-sskr, so I have:
- libbc-crypto-base.a
- libbc-shamir.a
- libbc-sskr.a

However when trying to build the docker image, the last step of the build stage fails with:
```
docker build -t seedtool-cli:latest .
...
41.53 /usr/bin/ld: /seedtool-cli/deps/bc-ur/src/ur.cpp:22: undefined reference to `std::__1::basic_string, std::__1::allocator >::~basic_string()'
41.54 /usr/bin/ld: /seedtool-cli/sysroot/lib/libbc-ur.a(random-sampler.o): in function `std::__1::vector >::__recommend(unsigned long) const':
41.54 /usr/lib/llvm-10/bin/../include/c++/v1/vector:1027: undefined reference to `std::__1::__vector_base_common::__throw_length_error() const'
41.54 /usr/bin/ld: /seedtool-cli/sysroot/lib/libbc-ur.a(random-sampler.o): in function `std::__1::vector >::__vallocate(unsigned long)':
41.54 /usr/lib/llvm-10/bin/../include/c++/v1/vector:993: undefined reference to `std::__1::__vector_base_common::__throw_length_error() const'
41.55 clang: error: linker command failed with exit code 1 (use -v to see invocation)
41.55 make[1]: *** [: seedtool] Error 1
41.55 make[1]: Leaving directory '/seedtool-cli/src'
41.55 make: *** [Makefile:38: check] Error 2
------
Dockerfile:18
--------------------
16 | WORKDIR /seedtool-cli
17 | RUN git submodule update --init --recursive
18 | >>> RUN CC="clang-10" CXX="clang++-10" ./build.sh
19 |
20 | # Export built executable to a minimal runtime image and run as an unprivileged
--------------------
ERROR: failed to solve: process "/bin/sh -c CC=\"clang-10\" CXX=\"clang++-10\" ./build.sh" did not complete successfully: exit code: 2
```