stage1: Another hack for the C ABI compatibility

Applying the wrong ABI is slightly better than using the Zig ABI, the
whole thing is so wrong it should be burned to the ground.

src/analyze.cpp

@@ -9044,7 +9044,7 @@ static void resolve_llvm_types_fn_type(CodeGen *g, ZigType *fn_type) {
     FnTypeId *fn_type_id = &fn_type->data.fn.fn_type_id;
     bool first_arg_return = want_first_arg_sret(g, fn_type_id);
     bool is_async = fn_type_id->cc == CallingConventionAsync;
-    bool is_c_abi = fn_type_id->cc == CallingConventionC;
+    bool is_c_abi = !calling_convention_allows_zig_types(fn_type_id->cc);
     bool prefix_arg_error_return_trace = g->have_err_ret_tracing && fn_type_can_fail(fn_type_id);
     // +1 for maybe making the first argument the return value
     // +1 for maybe first argument the error return trace

src/codegen.cpp

@@ -2071,7 +2071,7 @@ var_ok:
 
 void walk_function_params(CodeGen *g, ZigType *fn_type, FnWalk *fn_walk) {
     CallingConvention cc = fn_type->data.fn.fn_type_id.cc;
-    if (cc == CallingConventionC) {
+    if (!calling_convention_allows_zig_types(cc)) {
         size_t src_i = 0;
         for (;;) {
             if (!iter_function_params_c_abi(g, fn_type, fn_walk, src_i))
@@ -7862,7 +7862,7 @@ static void do_code_gen(CodeGen *g) {
 
         FnTypeId *fn_type_id = &fn_table_entry->type_entry->data.fn.fn_type_id;
         CallingConvention cc = fn_type_id->cc;
-        bool is_c_abi = cc == CallingConventionC;
+        bool is_c_abi = !calling_convention_allows_zig_types(cc);
         bool want_sret = want_first_arg_sret(g, fn_type_id);
 
         LLVMValueRef fn = fn_llvm_value(g, fn_table_entry);