[clang][driver][NFC] Add hasShadowCallStack to SanitizerArgs

Currently, we can't check if ShadowCallStack is present in Args the same
way we handle other sanitizers. This is preparatory work for planned
driver changes to how we handle ShadowCallStack.

Reviewed By: vitalybuka

Differential Revision: https://reviews.llvm.org/D148031

clang/include/clang/Driver/SanitizerArgs.h

@@ -119,6 +119,10 @@ public:
     return MemtagMode;
   }
 
+  bool hasShadowCallStack() const {
+    return Sanitizers.has(SanitizerKind::ShadowCallStack);
+  }
+
   bool requiresPIE() const;
   bool needsUnwindTables() const;
   bool needsLTO() const;