Build everything as C++ (#1176)

include/extern/getopt.hpp

@@ -26,9 +26,7 @@
 #ifndef RGBDS_EXTERN_GETOPT_H
 #define RGBDS_EXTERN_GETOPT_H
 
-#ifdef __cplusplus
 extern "C" {
-#endif
 
 extern char *musl_optarg;
 extern int musl_optind, musl_opterr, musl_optopt, musl_optreset;
@@ -47,8 +45,6 @@ int musl_getopt_long_only(int argc, char **argv, char const *optstring,
 #define required_argument  1
 #define optional_argument  2
 
-#ifdef __cplusplus
 } // extern "C"
-#endif
 
 #endif