Add UBSAN build option and fix undefined behaviour errors.

src/IceInstARM32.h

Index: src/IceInstARM32.h
diff --git a/src/IceInstARM32.h b/src/IceInstARM32.h
index 66d571236b9d0c64208b20cdb23f8b9d2ef3ca3c..6082f163e6eacd938ef2fb9880260e284dcecf54 100644
--- a/src/IceInstARM32.h
+++ b/src/IceInstARM32.h
@@ -36,7 +36,7 @@ class OperandARM32 : public Operand {
 
 public:
   enum OperandKindARM32 {
-    k__Start = Operand::kTarget,
+    k__Start = Operand::kTarget0,
     kMem,
     kFlexStart,
     kFlexImm = kFlexStart,
@@ -257,7 +257,7 @@ public:
     return new (Func->allocate<StackVariable>()) StackVariable(Ty, Index);
   }
   const static OperandKind StackVariableKind =
-      static_cast<OperandKind>(kVariable_Target);
+      static_cast<OperandKind>(kVariable_Target0);
   static bool classof(const Operand *Operand) {
     return Operand->getKind() == StackVariableKind;
   }
@@ -281,7 +281,7 @@ class InstARM32 : public InstTarget {
 
 public:
   enum InstKindARM32 {
-    k__Start = Inst::Target,
+    k__Start = Inst::Target0,
     Adc,
     Add,
     Adjuststack,