Add assembly test for the cmse unstable features

verifies that the correct return instructions are emitted.

Co-authored-by: Tamme Dittrich <tamme@tweedegolf.com>

tests/assembly/cmse.rs

@@ -0,0 +1,26 @@
+//@ assembly-output: emit-asm
+//@ compile-flags: --target thumbv8m.main-none-eabi --crate-type lib -Copt-level=1
+//@ needs-llvm-components: arm
+#![crate_type = "lib"]
+#![feature(abi_c_cmse_nonsecure_call, cmse_nonsecure_entry, no_core, lang_items)]
+#![no_core]
+#[lang = "sized"]
+pub trait Sized {}
+#[lang = "copy"]
+pub trait Copy {}
+
+// CHECK-LABEL: __acle_se_entry_point
+// CHECK: bxns
+#[no_mangle]
+pub extern "C-cmse-nonsecure-entry" fn entry_point() -> i64 {
+    0
+}
+
+// CHECK-LABEL: call_nonsecure
+// CHECK: blxns
+#[no_mangle]
+pub fn call_nonsecure(
+    f: unsafe extern "C-cmse-nonsecure-call" fn(u32, u32, u32, u32) -> u64,
+) -> u64 {
+    unsafe { f(0, 1, 2, 3) }
+}