libquiche.so undefined references

When I run curl's configure to try to use quiche from current git, I get these errors:

~~~
/usr/bin/ld: $path/libquiche.so: undefined reference to `__gxx_personality_v0'
/usr/bin/ld: $path/libquiche.so: undefined reference to `vtable for __cxxabiv1::__si_class_type_info'
/usr/bin/ld: $path/libquiche.so: undefined reference to `operator delete(void*, unsigned long)'
/usr/bin/ld: $path/libquiche.so: undefined reference to `vtable for __cxxabiv1::__class_type_info'

~~~
(`$path` is me hiding my local long path to make it easier to the eye)

Any clues on what I am missing? (These looks like traces of C++, which I suspected might come from BoringSSL, but I am able to build from current BoringSSL without getting this problem.)

Start with curl's configure invocation that links against the current-git libquiche.so, then inspect the shared library's unresolved symbols and native link dependencies. Compare that link step with the successful BoringSSL build; done means curl configures and links without the reported C++ runtime references.

Written by the indexing model from the issue text.