Add flag to enable Dwarf exception handling on ARM

lib/Target/ARM/ARMSubtarget.h

Index: lib/Target/ARM/ARMSubtarget.h
diff --git a/lib/Target/ARM/ARMSubtarget.h b/lib/Target/ARM/ARMSubtarget.h
index f646f1537b7cebc37f8f94438085720be53650e1..0f8e66e7b92ded54ce7c776abd3d3e1ab8696dde 100644
--- a/lib/Target/ARM/ARMSubtarget.h
+++ b/lib/Target/ARM/ARMSubtarget.h
@@ -40,6 +40,8 @@ class GlobalValue;
 class StringRef;
 class TargetOptions;
 
+extern cl::opt<bool>  EnableARMDwarfEH; // @LOCALMOD
+
 class ARMSubtarget : public ARMGenSubtargetInfo {
 protected:
   enum ARMProcFamilyEnum {
@@ -383,7 +385,8 @@ public:
             TargetTriple.getEnvironment() == Triple::EABIHF ||
             TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
             TargetTriple.getEnvironment() == Triple::Android) &&
-           !isTargetDarwin() && !isTargetWindows();
+        !isTargetDarwin() && !isTargetWindows() &&
+        !isTargetNaCl() && !EnableARMDwarfEH; // @LOCALMOD
   }
 
   bool isTargetHardFloat() const {