wrappers: Stop explicitly requesting SEH for AArch64

It is the default exception handling model there now.

wrappers/clang-target-wrapper.c

@@ -179,7 +179,7 @@ int _tmain(int argc, TCHAR* argv[]) {
     } else if (!_tcscmp(arch, _T("armv7"))) {
         // Dwarf is the default here.
     } else if (!_tcscmp(arch, _T("aarch64"))) {
-        exec_argv[arg++] = _T("-fseh-exceptions");
+        // SEH is the default here.
     }
 
     if (target_os && !_tcscmp(target_os, _T("mingw32uwp"))) {

wrappers/clang-target-wrapper.sh

@@ -46,7 +46,7 @@ armv7)
     # Dwarf is the default here.
     ;;
 aarch64)
-    FLAGS="$FLAGS -fseh-exceptions"
+    # SEH is the default here.
     ;;
 esac
 case $TARGET_OS in