add rp6502 target

libsrc/rp6502/open.c

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+#include <string.h>
+
+int __cdecl__ open(const char *name, int flags, ...)
+{
+    size_t namelen = strlen(name);
+    if (namelen > 255)
+    {
+        return _mappederrno(EINVAL);
+    }
+    while (namelen)
+    {
+        ria_push_char(name[--namelen]);
+    }
+    ria_set_ax(flags);
+    return ria_call_int_errno(RIA_OP_OPEN);
+}