Cannot compile on v7.0 #1173
Description
Both gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609 and
clang version 6.0.0-1ubuntu2~16.04.1 (tags/RELEASE_600/final) failed to compile and report this error.
or-tools/ortools/linear_solver/linear_solver.h:731:13: error: use of
overloaded operator '<<' is ambiguous (with operand types 'std::ostream' (aka 'basic_ostream<char>') and
'const absl::string_view')