This deletes our old branches of internal Abseil code in favor of their newly open-sourced library. Notably, this removes the ability to turn CHECK crashes into exceptions.
PiperOrigin-RevId: 504460562
* Do not force C++14
Rather than forcing protobuf to always compile in exactly C++14, overriding all settings in .bazelrc and environment variables and commandline options, instead guard the codebase against versions that are too low. This allows for compiling in higher C++ standards, such as those that have std::string_view instead of absl::string_view without generating objects that are incompatible.
* Do not guard headers against low C++ versions
The code will break below C++14 anyway
* Attempt a different >=C++14 guard condition
* Steal the >=C++14 guard condition code from absl
* Special case C++14 guard for GCC < 5.0
* Enable warnings as errors by default for test builds
* Fixing C++ warnings
* Adding host flags, and enabling warnings as error for non-C++ too
* Switch to BUILD copts instead of bazelrc to treat Windows as a snowflake
* Disable warnings as errors on Windows, since it doesn't like the c++14 flag
These are all "toolchain-y" things, like copts, link_opts, and config_settings. These are very different from what is in //toolchain, though, so I chose the somewhat common name build_defs for the package. For now, I am only using this package for purely internal things. (Most public "defs"-type things should come from rules_proto/rules_cc, anyhow.)