don't use no_main and no_core to test IBT

Author: jyn514

tests/run-make/branch-protection-check-IBT/lib.rs

@@ -0,0 +1 @@
+#![no_std]

tests/run-make/branch-protection-check-IBT/main.rs

@@ -43,11 +43,13 @@ use run_make_support::{bare_rustc, llvm_readobj};
 fn main() {
     // `main.rs` is `#![no_std]` to not pull in the currently not-compiled-with-IBT precompiled std.
     bare_rustc()
-        .input("main.rs")
+        .input("lib.rs")
+        .crate_type("lib")
+        .emit("obj=lib.o")
         .target("x86_64-unknown-linux-gnu")
         .arg("-Zcf-protection=branch")
         .arg("-Clink-args=-nostartfiles")
         .run();
 
-    llvm_readobj().arg("-nW").input("main").run().assert_stdout_contains(".note.gnu.property");
+    llvm_readobj().arg("-nW").input("lib.o").run().assert_stdout_contains(".note.gnu.property");
 }