Without this patch, libm will be linked before libgcc (which is a linker script that links to both libunwind and libgcc_real); as libm.so in our system exports unwind symbols, it prevents the built objects from being linked to the unwinders properly.
Since libm is a part of bionic, we can't ship it like we do for libc++_shared or zlib. Therefore, patching clang++ is probably the only way.
Tom Yan