CFI: Add missing use core::ffi::c_int

Adds missing use core::ffi::c_int for when
sanitizer_cfi_normalize_integers is defined.

Author: rcvalle

library/std/src/sys/unix/thread_local_dtor.rs

@@ -4,6 +4,8 @@
 //! Provides thread-local destructors without an associated "key", which
 //! can be more efficient.
 
+use core::ffi::c_int;
+
 // Since what appears to be glibc 2.18 this symbol has been shipped which
 // GCC and clang both use to invoke destructors in thread_local globals, so
 // let's do the same!