Fix build of thumbv7a-pc-windows-msvc

Author: arlosi

library/panic_unwind/src/lib.rs

@@ -42,7 +42,8 @@ cfg_if::cfg_if! {
         // L4Re is unix family but does not yet support unwinding.
         #[path = "dummy.rs"]
         mod real_imp;
-    } else if #[cfg(target_env = "msvc")] {
+    } else if #[cfg(all(target_env = "msvc", not(target_arch = "arm")))] {
+        // LLVM does not support unwinding on 32 bit ARM msvc (thumbv7a-pc-windows-msvc)
         #[path = "seh.rs"]
         mod real_imp;
     } else if #[cfg(any(