build fails

Using `tools/build.sh --clang` and `--gcc` on Debian Bullseye.
Error is from using `--clang`.
GDK 0.0.47

```
[3/4] Linking target src/libgreenaddress.so
FAILED: src/libgreenaddress.so
clang++ -o src/libgreenaddress.so src/libgreenaddress.so.p/amount.cpp.o src/libgreenaddress.so.p/assertion.cpp.o src/libgreenaddress.so.p/auth_handler.cpp.o src/libgreenaddress.so.p/client_blob.cpp.o src/libgreenaddress.so.p/containers.cpp.o src/libgreenaddress.so.p/exception.cpp.o src/libgreenaddress.so.p/ffi_c.cpp.o src/libgreenaddress.so.p/ga_auth_handlers.cpp.o src/libgreenaddress.so.p/ga_cache.cpp.o src/libgreenaddress.so.p/ga_session.cpp.o src/libgreenaddress.so.p/ga_strings.cpp.o src/libgreenaddress.so.p/ga_tor.cpp.o src/libgreenaddress.so.p/ga_tx.cpp.o src/libgreenaddress.so.p/ga_wally.cpp.o src/libgreenaddress.so.p/http_client.cpp.o src/libgreenaddress.so.p/inbuilt.cpp.o src/libgreenaddress.so.p/network_parameters.cpp.o src/libgreenaddress.so.p/session.cpp.o src/libgreenaddress.so.p/session_impl.cpp.o src/libgreenaddress.so.p/signer.cpp.o src/libgreenaddress.so.p/socks_client.cpp.o src/libgreenaddress.so.p/sqlite3_sqlite3.c.o src/libgreenaddress.so.p/transaction_utils.cpp.o src/libgreenaddress.so.p/utils.cpp.o src/libgreenaddress.so.p/xpub_hdkey.cpp.o -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -shared -fPIC -Wl,--start-group -Wl,-soname,libgreenaddress.so -fuse-ld=gold -ldl -Wl,-z,now -Wl,-z,relro -Wl,-z,noexecstack -Wl,--whole-archive /home/user/builds/gdk/build-clang/libwally-core/build/lib/libwallycore.a -Wl,--no-whole-archive /home/user/builds/gdk/build-clang/libwally-core/build/lib/libsecp256k1.a /home/user/builds/gdk/build-clang/boost/build/lib/libboost_chrono.a /home/user/builds/gdk/build-clang/boost/build/lib/libboost_date_time.a /home/user/builds/gdk/build-clang/boost/build/lib/libboost_log.a /home/user/builds/gdk/build-clang/boost/build/lib/libboost_system.a /home/user/builds/gdk/build-clang/boost/build/lib/libboost_thread.a /home/user/builds/gdk/build-clang/openssl/build/lib/libssl.a /home/user/builds/gdk/build-clang/openssl/build/lib/libcrypto.a /home/user/builds/gdk/build-clang/zlib/libz.a /home/user/builds/gdk/build-clang/libevent/build/lib/libevent_core.a /home/user/builds/gdk/build-clang/libevent/build/lib/libevent_pthreads.a /home/user/builds/gdk/build-clang/libevent/build/lib/libevent_extra.a /home/user/builds/gdk/build-clang/tor/src/core/libtor-app.a /home/user/builds/gdk/build-clang/tor/src/ext/ed25519/donna/libed25519_donna.a /home/user/builds/gdk/build-clang/tor/src/ext/ed25519/ref10/libed25519_ref10.a /home/user/builds/gdk/build-clang/tor/src/ext/keccak-tiny/libkeccak-tiny.a /home/user/builds/gdk/build-clang/tor/src/lib/libcurve25519_donna.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-buf.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-compress.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-confmgt.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-container.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-crypt-ops.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-ctime.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-dispatch.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-encoding.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-err.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-evloop.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-fdio.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-fs.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-geoip.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-intmath.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-lock.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-log.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-malloc.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-math.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-memarea.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-meminfo.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-net.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-osinfo.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-pubsub.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-sandbox.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-smartlist-core.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-string.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-term.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-thread.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-time.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-tls.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-trace.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-version.a /home/user/builds/gdk/build-clang/tor/src/lib/libtor-wallclock.a /home/user/builds/gdk/build-clang/tor/src/trunnel/libor-trunnel.a -pthread -lm -latomic -Wl,--end-group
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function have_capability_support: error: undefined reference to 'cap_get_proc'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function have_capability_support: error: undefined reference to 'cap_free'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_get_proc'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_clear'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_set_flag'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_set_flag'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_set_flag'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_set_proc'
/home/user/builds/gdk/build-clang/tor/src/lib/libtor-process.a(setuid.o):setuid.c:function drop_capabilities: error: undefined reference to 'cap_free'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
```