This happens when testing the next version of llvm with libc++: https://logs.chromium.org/v/?s=chromeos%2Fbb%2Fchromiumos.tryserver%2Fchromiumos-sdk%2F2836%2F%2B%2Frecipes%2Fsteps%2FInitSDK%2F0%2Fstdout

In the host sdk, dev-util/ragel build fails with new error:

ragel-6.7-r3: rbxgoto.cpp:661:8: error: invalid operands to binary expression
ragel-6.7-r3:       ('basic_ostream<char, std::__1::char_traits<char> >' and
ragel-6.7-r3:       'std::__1::ostream' (aka 'basic_ostream<char>'))
ragel-6.7-r3:                 "               " << rbxGoto(ret, "_out") << "\n" 
ragel-6.7-r3:                 ~~~~~~~~~~~~~~~~~ ^  ~~~~~~~~~~~~~~~~~~~~
ragel-6.7-r3: /usr/bin/../include/c++/v1/ostream:220:20: note: candidate function not viable:
ragel-6.7-r3:       no known conversion from 'std::__1::ostream' (aka 'basic_ostream<char>')
ragel-6.7-r3:       to 'const void *' for 1st argument; take the address of the argument with
ragel-6.7-r3:       &
ragel-6.7-r3:     basic_ostream& operator<<(const void* __p);
ragel-6.7-r3:                    ^
ragel-6.7-r3: /usr/bin/../include/c++/v1/ostream:196:20: note: candidate function not viable:
ragel-6.7-r3:       no known conversion from 'std::__1::ostream' (aka 'basic_ostream<char>')
ragel-6.7-r3:       to 'std::__1::basic_ostream<char, std::__1::char_traits<char> >
ragel-6.7-r3:       &(*)(std::__1::basic_ostream<char, std::__1::char_traits<char> > &)' for
ragel-6.7-r3:       1st argument
ragel-6.7-r3:     basic_ostream& operator<<(basic_ostream& (*__pf)(basic_ostream&))
ragel-6.7-r3:                    ^
...

The other errors [-Wc++11-narrowing] are from llvm-next, but I suspect that this error is due to libc++.