Fix rustc test suite

Author: bjorn3

scripts/test_rustc_tests.sh

@@ -45,6 +45,7 @@ rm -r tests/run-make/naked-symbol-visibility
 rm tests/ui/abi/mir/mir_codegen_calls_variadic.rs # requires float varargs
 rm tests/ui/abi/variadic-ffi.rs # requires callee side vararg support
 rm -r tests/run-make/c-link-to-rust-va-list-fn # requires callee side vararg support
+rm tests/ui/c-variadic/valid.rs # same
 rm tests/ui/delegation/fn-header.rs
 
 # misc unimplemented things