linux: store configuration in $XDG_DATA_HOME

Store configuration in $XDG_DATA_HOME. If unavailable,
default to $HOME/.local/share .

Author: whizikxd

src/os/core/linux/os_core_linux.c

@@ -1573,8 +1573,17 @@ main(int argc, char **argv)
 
       // rjf: grab home directory
       {
-        char *home = getenv("HOME");
-        info->user_program_data_path = str8_cstring(home);
+        char *data_home = getenv("XDG_DATA_HOME");
+        if (data_home == 0 ||
+            cstring8_length((U8 *)data_home) == 0) {
+          // default to $HOME/.local/share (https://specifications.freedesktop.org/basedir/latest/#variables)
+          data_home = getenv("HOME");
+          info->user_program_data_path = push_str8f(os_lnx_state.arena, "%S/%S",
+                                                    str8_cstring(data_home),
+                                                    str8_lit(".local/share"));
+        } else {
+          info->user_program_data_path = str8_cstring(data_home);
+        }
       }
 
       scratch_end(scratch);