[build] adding libpostal_setup_datadir, libpostal_setup_parser_datadir, libpostal_setup_language_classifier_datadir functions for configuring the datadir at runtime

src/file_utils.h

@@ -9,6 +9,7 @@
 #include <sys/types.h>
 
 #include "libpostal_config.h"
+#include "string_utils.h"
 
 #ifdef HAVE_DIRENT_H
 #include <dirent.h>
@@ -55,6 +56,9 @@ char *file_getline(FILE * f);
 
 bool is_relative_path(struct dirent *ent);
 
+char *path_join(int n, ...);
+char *path_vjoin(int n, va_list args);
+
 uint64_t file_deserialize_uint64(unsigned char *buf);
 bool file_read_uint64(FILE *file, uint64_t *value);
 bool file_write_uint64(FILE *file, uint64_t value);