The CMake build already adds -Wundef for gcc/clang. This change makes sure that
the gcc/clang Bazel builds also compile correctly with -Wundef (#3267).
PiperOrigin-RevId: 514864451
Change-Id: I7798a4a4c68d037e23625db24ee29df454367734
v1.12.x is the last branch to support C++11
Future releases will require at least C++14
PiperOrigin-RevId: 458250106
Change-Id: Ibee2248649ff3c13daaa179135887848bf730f3f