regression: `brew install grpc` fails: bad reloc symbol index

[timotheecour]

brew install grpc

collect2: fatal error: ld terminated with signal 11 [Segmentation fault]
compilation terminated.
brew/bin/ld: /tmp/grpc-20170703-35063-1r0qmbs/grpc-1.4.1/libs/opt/libgpr.a(basic_timers.o): bad reloc symbol index (0x6d69745f >= 0x12) for offset 0x0 in section `.debug_info'

FYI @stanley-cheung this looks like a regression, grpc worked when #96 was closed

This also fails:

brew install grpc/grpc/grpc
undefined reference to `google::protobuf::MethodDescriptor::output_type() const