add rp6502 target

libsrc/rp6502/close.c

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+
+int __fastcall__ close(int fd)
+{
+    ria_set_ax(fd);
+    return ria_call_int_errno(RIA_OP_CLOSE);
+}