Add cross-language LLVM CFI support to the Rust compiler

This commit adds cross-language LLVM Control Flow Integrity (CFI)
support to the Rust compiler by adding the
`-Zsanitizer-cfi-normalize-integers` option to be used with Clang
`-fsanitize-cfi-icall-normalize-integers` for normalizing integer types
(see https://reviews.llvm.org/D139395).

It provides forward-edge control flow protection for C or C++ and Rust
-compiled code "mixed binaries" (i.e., for when C or C++ and Rust
-compiled code share the same virtual address space). For more
information about LLVM CFI and cross-language LLVM CFI support for the
Rust compiler, see design document in the tracking issue #89653.

Cross-language LLVM CFI can be enabled with -Zsanitizer=cfi and
-Zsanitizer-cfi-normalize-integers, and requires proper (i.e.,
non-rustc) LTO (i.e., -Clinker-plugin-lto).

compiler/rustc_span/src/symbol.rs

@@ -443,6 +443,7 @@ symbols! {
         c_str,
         c_unwind,
         c_variadic,
+        c_void,
         call,
         call_mut,
         call_once,
@@ -470,6 +471,7 @@ symbols! {
         cfg_target_vendor,
         cfg_version,
         cfi,
+        cfi_encoding,
         char,
         client,
         clippy,
@@ -1319,6 +1321,8 @@ symbols! {
         s,
         safety,
         sanitize,
+        sanitizer_cfi_generalize_pointers,
+        sanitizer_cfi_normalize_integers,
         sanitizer_runtime,
         saturating_add,
         saturating_sub,