[compiler-rt][ubsan][nfc-ish] Fix a type conversion bug (llvm#100665)

If the inline asm version of `ptrauth_strip` is used instead of the
builtin, the inline asm implementation currently returns an unsigned
long, causing an incompatible pointer conversion issue. The spec for
`ptrauth_sign` is that the result has the same type as the original
value, so we add a cast to the result of the inline asm.

Author: alanzhao1

compiler-rt/lib/sanitizer_common/sanitizer_ptrauth.h

@@ -18,7 +18,7 @@
 // the NOP space so will do nothing when it is not enabled or not available.
 #  define ptrauth_strip(__value, __key) \
     ({                                  \
-      unsigned long ret;                \
+      __typeof(__value) ret;            \
       asm volatile(                     \
           "mov x30, %1\n\t"             \
           "hint #7\n\t"                 \