Build everything as C++ (#1176)

include/extern/getopt.hpp

@@ -0,0 +1,50 @@
+/*
+ * Copyright © 2005-2020 Rich Felker, et al.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/* This implementation was taken from musl and modified for RGBDS */
+
+#ifndef RGBDS_EXTERN_GETOPT_H
+#define RGBDS_EXTERN_GETOPT_H
+
+extern "C" {
+
+extern char *musl_optarg;
+extern int musl_optind, musl_opterr, musl_optopt, musl_optreset;
+
+struct option {
+	char const *name;
+	int has_arg;
+	int *flag;
+	int val;
+};
+
+int musl_getopt_long_only(int argc, char **argv, char const *optstring,
+			  const struct option *longopts, int *idx);
+
+#define no_argument        0
+#define required_argument  1
+#define optional_argument  2
+
+} // extern "C"
+
+#endif