These are the critical internal libs from gcc needed in order to bootstrap new
glibc shared libs.  It's merely a precompiled version of gcc.

Note, for glibc-2.26 and later we need gcc-6.

How was this tarball generated?

* Collect current stage3 autobuilds, ideally for
    amd64, mips, ppc, s390, x86
  (but in practice the stable subset will do)

* Copy files from, e.g., 
  /usr/lib64/gcc/x86_64-pc-linux-gnu/6.4.0/
  to amd64 

  The full list of directory names is:
  amd64  n32  n64  o32  ppc  ppc64  s390  s390x  x32  x86

* At the end run ./Cleanup to remove everything that is not needed


Current status: 

* amd64, x32, x86: Files from gcc-6.4
* s390, s390x: Files from gcc-5.4 (does this work?)
* ppc, ppc64: no files, since only gcc-4.9 available
* n32, n64, o32: last mips stages are years old, not useful
