Subzero: Fix a build error against LLVM trunk.

LLVM commit 1d79fff9e65e77f84bf80c2cf4f0155bd167c90d changed the way ilist::reverse_iterator is converted to ilist::iterator.

See https://github.com/llvm-mirror/llvm/commit/1d79fff9e65e77f84bf80c2cf4f0155bd167c90d

BUG= none
R=kschimpf@google.com

Review URL: https://codereview.chromium.org/2297363002 .
diff --git a/src/IceTargetLoweringARM32.cpp b/src/IceTargetLoweringARM32.cpp
index 0add99a..7564652 100644
--- a/src/IceTargetLoweringARM32.cpp
+++ b/src/IceTargetLoweringARM32.cpp
@@ -1703,7 +1703,7 @@
 
   // Convert the reverse_iterator position into its corresponding (forward)
   // iterator position.
-  InstList::iterator InsertPoint = RI.base();
+  InstList::iterator InsertPoint = reverseToForwardIterator(RI);
   --InsertPoint;
   Context.init(Node);
   Context.setInsertPoint(InsertPoint);