Fix host_arch detection for AIX and one new warning as error

src/hydrogen-bce.cc

Index: src/hydrogen-bce.cc
diff --git a/src/hydrogen-bce.cc b/src/hydrogen-bce.cc
index 3bf8e9f03904c76ca9ee406cf5a4dbfed517148b..9d634a8fa84f02654fb7179c2cdb91487ee54609 100644
--- a/src/hydrogen-bce.cc
+++ b/src/hydrogen-bce.cc
@@ -380,7 +380,7 @@ BoundsCheckBbData* HBoundsCheckEliminationPhase::PreProcessBlock(
     if (!i->IsBoundsCheck()) continue;
 
     HBoundsCheck* check = HBoundsCheck::cast(i);
-    int32_t offset;
+    int32_t offset = 0;
     BoundsCheckKey* key =
         BoundsCheckKey::Create(zone(), check, &offset);
     if (key == NULL) continue;