add test that tracks that functions defined in extern blocks are not exported

this maybe should change, but now at least it won't be changed unintentionally

Author: folkertdev

tests/run-make/naked-symbol-visibility/a_rust_dylib.rs

@@ -72,3 +72,16 @@ extern "C" fn naked_weak_linkage() -> u32 {
 extern "C" fn naked_external_linkage() -> u32 {
     unsafe { asm!("mov rax, 42", "ret", options(noreturn)) }
 }
+
+// functions that are declared in an `extern "C"` block are currently not exported
+// this maybe should change in the future, this is just tracking the current behavior
+// reported in https://github.com/rust-lang/rust/issues/128071
+std::arch::global_asm! {
+    ".globl function_defined_in_global_asm",
+    "function_defined_in_global_asm:",
+    "ret",
+}
+
+extern "C" {
+    pub fn function_defined_in_global_asm();
+}

tests/run-make/naked-symbol-visibility/rmake.rs

@@ -25,6 +25,11 @@ fn main() {
     rustc().arg("-Zshare-generics=yes").input("a_rust_dylib.rs").run();
     global_function(&rdylib_name, "public_vanilla_generic_function_from_rust_dylib");
     global_function(&rdylib_name, "public_naked_generic_function_from_rust_dylib");
+
+    // functions that are declared in an `extern "C"` block are currently not exported
+    // this maybe should change in the future, this is just tracking the current behavior
+    // reported in https://github.com/rust-lang/rust/issues/128071
+    not_exported(&rdylib_name, "function_defined_in_global_asm");
 }
 
 #[track_caller]