LoopVectorize: Simplify code. No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220405 91177308-0d34-0410-b5e6-96231b3b80d8
Do not add -gsplit-dwarf to LLVM_DEFINITIONS.

This would cause the flag to appear in the output of "llvm-config --cppflags",
which should contain only preprocessor flags. The -gsplit-dwarf flag in
particular can cause problems with certain downstream users such as cgo.

Differential Revision: http://reviews.llvm.org/D5895

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220410 91177308-0d34-0410-b5e6-96231b3b80d8