Allow disabling ASan instrumentation for globals

AddressSanitizer adds instrumentation to global variables unless the
[`no_sanitize_address`](https://llvm.org/docs/LangRef.html#global-attributes)
attribute is set on them.

This commit extends the existing `#[no_sanitize(address)]` attribute to
set this; previously it only had the desired effect on functions.

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2474,4 +2474,7 @@ unsafe extern "C" {
     pub fn LLVMRustIs64BitSymbolicFile(buf_ptr: *const u8, buf_len: usize) -> bool;
 
     pub fn LLVMRustIsECObject(buf_ptr: *const u8, buf_len: usize) -> bool;
+
+    pub fn LLVMRustSetNoSanitizeAddress(Global: &Value);
+    pub fn LLVMRustSetNoSanitizeHWAddress(Global: &Value);
 }