Revert "Auto merge of #65134 - davidtwco:issue-19834-improper-ctypes-in-extern-C-fn, r=rkruppe"

This reverts commit 3f0e16473d, reversing
changes made to 61a551b493.

src/librustc_codegen_llvm/back/write.rs

@@ -240,7 +240,9 @@ impl<'a> Drop for DiagnosticHandlers<'a> {
     }
 }
 
-fn report_inline_asm(cgcx: &CodegenContext<LlvmCodegenBackend>, msg: &str, cookie: c_uint) {
+unsafe extern "C" fn report_inline_asm(cgcx: &CodegenContext<LlvmCodegenBackend>,
+                                       msg: &str,
+                                       cookie: c_uint) {
     cgcx.diag_emitter.inline_asm_error(cookie as u32, msg.to_owned());
 }