Disable enumeral mismatch warning when compiling llvm with gcc.

Tested with gcc 4.9.2.
Compiling with -Werror was producing:
.../llvm/lib/Target/X86/X86ISelLowering.cpp: In function 'llvm::SDValue lowerVectorShuffleAsBitMask(llvm::SDLoc, llvm::MVT, llvm::SDValue, llvm::SDValue, llvm::ArrayRef<int>, llvm::SelectionDAG&)':
.../llvm/lib/Target/X86/X86ISelLowering.cpp:7771:40: error: enumeral mismatch in conditional expression: 'llvm::X86ISD::NodeType' vs 'llvm::ISD::NodeType' [-Werror=enum-compare]
   V = DAG.getNode(VT.isFloatingPoint() ? X86ISD::FAND : ISD::AND, DL, VT, V,
                                        ^

llvm-svn: 228271