This patch adds support for building libsupc++ (the C++ runtime
support library from GCC's libstdc++-v3).
libsupc++ provides core C++ runtime support including:
- Exception handling (eh_*.cc)
- RTTI (Run-Time Type Information)
- Memory allocation operators (new/delete)
- Type info support
The implementation includes:
- libsupc++.defs for libsupc++ build integration
- support make and cmake build
- Use gthr.h, gthr-posix.h and unwind-pe.h from libgcc
- LIBSTDCXX_VERSION config option with default 14.2.0
Signed-off-by: cuiziwei <cuiziwei@xiaomi.com>
