[libc++abi] Disable _Unwind_ForcedUnwind + exception tests for ARM EHABI

libunwind ARM EHABI does not support _Unwind_ForcedUnwind yet.
In addition, ARM EHABI makes `_Unwind_Exception` a typedef so
`struct _Unwind_Exception*` cannot be used.

Author: MaskRay

libcxxabi/test/forced_unwind1.pass.cpp

@@ -16,6 +16,9 @@
 #include <unwind.h>
 #include <tuple>
 
+#if defined(_LIBCXXABI_ARM_EHABI)
+int main() {}
+#else
 static int bits = 0;
 
 struct C {
@@ -75,3 +78,4 @@ int main() {
   test();
   return bits != 15;
 }
+#endif

libcxxabi/test/forced_unwind2.pass.cpp

@@ -17,6 +17,9 @@
 #include <unwind.h>
 #include <tuple>
 
+#if defined(_LIBCXXABI_ARM_EHABI)
+int main() {}
+#else
 template <typename T>
 struct Stop;
 
@@ -55,3 +58,4 @@ int main() {
   }
   abort();
 }
+#endif