Blacklist Apple clang 3.0 and previous support for AVX

Blacklist Apple clang 3.0 and previous support for AVX

In at least one case found in our testfarm, the compiler runs into an
ICE (Internal Compiler Error) compiling the new AVX code. The error it
reported was:

 fatal error: error in backend: Cannot select: 0x7fbf1aa42210: f64 = sint_to_fp 0x7fbf1aa88a10 [ORD=1936] [ID=37]
   0x7fbf1aa88a10: i32,ch = CopyFromReg 0x7fbf19538768, 0x7fbf1a9f2610 [ORD=1936] [ID=27]
     0x7fbf1a9f2610: i32 = Register %vreg38 [ORD=1936] [ID=9]

As is the nature of ICEs, juggling the code around will probably make
it pass. But since I have plenty more AVX changes pending, which make
the code even more complex, it's also very likely that this issue will
happen in other places. For that reason, I choose to blacklist the
compiler instead.

Change-Id: Ide3201f0cc49c7ceb63e966f6de65a8315cbea4b
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@nokia.com>