remove support for the #[start] attribute

tests/codegen/gdb_debug_script_load.rs

@@ -4,14 +4,34 @@
 //@ ignore-wasm
 //@ ignore-emscripten
 
-//@ compile-flags: -g -C no-prepopulate-passes
+//@ compile-flags: -g -C no-prepopulate-passes -Cpanic=abort
 
-#![feature(start)]
+#![feature(lang_items)]
+#![no_std]
 
+#[panic_handler]
+fn panic_handler(_: &core::panic::PanicInfo) -> ! {
+    loop {}
+}
+
+#[no_mangle]
+extern "C" fn rust_eh_personality() {
+    loop {}
+}
+
+// Needs rustc to generate `main` as that's where the magic load is inserted.
+// IOW, we cannot write this test with `#![no_main]`.
 // CHECK-LABEL: @main
 // CHECK: load volatile i8, {{.+}} @__rustc_debug_gdb_scripts_section__
 
-#[start]
-fn start(_: isize, _: *const *const u8) -> isize {
+#[lang = "start"]
+fn lang_start<T: 'static>(
+    _main: fn() -> T,
+    _argc: isize,
+    _argv: *const *const u8,
+    _sigpipe: u8,
+) -> isize {
     return 0;
 }
+
+fn main() {}