add support for targeting glibc 2.34

[andrewrk]

Previous release issue: #4459

glibc 2.34 was released. Time to follow the update procedure.

This bit is particularly interesting:

Major new features:

• In order to support smoother in-place-upgrades and to simplify
  the implementation of the runtime all functionality formerly
  implemented in the libraries libpthread, libdl, libutil, libanl has
  been integrated into libc. New applications do not need to link with
  -lpthread, -ldl, -lutil, -lanl anymore. For backwards compatibility,
  empty static archives libpthread.a, libdl.a, libutil.a, libanl.a are
  provided, so that the linker options keep working. Applications which
  have been linked against glibc 2.33 or earlier continue to load the
  corresponding shared objects (which are now empty). The integration
  of those libraries into libc means that additional symbols become
  available by default. This can cause applications that contain weak
  references to take unexpected code paths that would only have been
  used in previous glibc versions when e.g. preloading libpthread.so.0,
  potentially exposing application bugs.

This one might affect our logic for detecting glibc version:

• Previously, glibc installed its various shared objects under versioned
  file names such as libc-2.33.so. The ABI sonames (e.g., libc.so.6)
  were provided as symbolic links. Starting with glibc 2.34, the shared
  objects are installed under their ABI sonames directly, without
  symbolic links. This increases compatibility with distribution
  package managers that delete removed files late during the package
  upgrade or downgrade process.