firebase-ios-sdk

Fix the build on Windows (#4384)

* Fix errors about Abseil using std::copy

The C++11 version of this function can be unsafe if used improperly.
Defining this macro is also done in the Abseil build, though they don't
export the setting.

* Prevent output differences in generated certificate data

* Don't regenerate nanopb sources on Windows

There's something wrong with the interaction between protoc and the
nanopb generator that prevents this from working properly.