[3.8 Release] RC2 has been tagged

Here's a quick update

clang+llvm-3.8.0-rc2-x86_64-linux-gnu-debian8.tar.xz (sha1sum:
    All ok
  Cross compiling to various MIPS targets:
    16 out of 23 configs passed
    1 out of the remaining 7 failed a small number of tests with a
timeout. I expect these will pass when I re-run them.
    Remaining 6 configs still running...

For cross-compilation, it's now 22 out of 23 passing. The remaining config had fewer timeouts on the re-run but not all of them went away. I'm re-running the last two timeouts while my machine is less busy.

clang+llvm-3.8.0-rc2-mips-linux-gnu.tar.xz (sha1sum:
  Failed to run check-all due to tsan'd libc++ build failing
    PR26278 - My fix for this was committed just after the rc2 tag
so in order to get some check-all results, I applied those four patches
(r25966[1456]) and re-ran check-all.
    PR26369 - Several failures related to the lack of -latomic
which is needed for 64-bit atomics.
    PR26476 - One new failure in libc++ (I probably just missed it
amongst the others). Apparently std::regex_traits says that '-' doesn't belong
to the 'w' class but only on big-endian.
    check-all appears to hang at 99%. I'll look into this.
  LNT (using the clean rc2)
    1 of 3 passed successfully, the other two are still running

LNT finished successfully and everything passed.

I've identified the hanging test. It's a mips64 msan test so I'm planning to mark it UNSUPPORTED (XFAIL will still hang) since this isn't a regression on the last release.

We're still investigating PR26476, and we're also trying to get PR26369 committed+merged.

> clang+llvm-3.8.0-rc2-mipsel-linux-gnu.tar.xz (sha1sum:

  Build almost ok. I only have failures related to PR26369.
  LNT just started.

All ok aside from PR26369.