[ADT] Just give up on GCC, I can't fix this.

While the memmove workaround fixed it for GCC 6.3. GCC 4.8 and GCC 7.1
are still broken. I have no clue what's going on, just blacklist GCC for
now.

Needless to say this code is ubsan, asan and msan-clean.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@322862 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed