[llvm-exegesis] Fix compile error on VS.
llvm::BitVector::const_set_bits_iterator is not formally a
ForwardIterator. Using it as such results in compile time errors on some
compilers:
FAILED: unittests/tools/llvm-exegesis/X86/CMakeFiles/LLVMExegesisX86Tests.dir/RegisterAliasingTest.cpp.obj
C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\INCLUDE\xutility(967): error C2794: 'iterator_category': is not a member of any direct or indirect base class of 'std::iterator_traits<_InIt>'
with
[
_InIt=llvm::BitVector::const_set_bits_iterator
]
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@332697
91177308-0d34-0410-b5e6-
96231b3b80d8