### Godot version

any version after 74458b6

### System information

Linux x64, but likely irrelevant

### Issue description

OpenXR action maps are not properly exported in recent builds of Godot 4: the `.res` file is small and does no longer seem to contain anything of use. In-game, no actions are passed on to OpenXR (obviously).

I bisected the issue down to https://github.com/godotengine/godot/commit/74458b6e9bed0f28db3374c7406eacbcf4b09b9d, which was merged in #70377.

### Steps to reproduce

1. Delete any previous export files (`.godot/exported/*/*.pkg`)
2. Perform an export (I did one for Android, but it likely works with anything)
3. Observe OpenXR actions not working in the export (error spam 'sync_action_sets: Condition "active_sets.size() == 0"'), and the exported action map file being very small (`.godot/exported/*/*.pkg`, from a few tens of kilobytes down to 296 bytes)

### Minimal reproduction project

Any OpenXR project can be used, such as https://github.com/BastiaanOlij/godot4_openxr_demo
v |= ct << 4;
				}
				if (i * 2 + 1 < script_key.length()) {
					char32_t ct = script_key[i * 2 + 1];
					if (is_digit(ct)) {
						ct = ct - '0';
					} else if (ct >= 'a' && ct <= 'f') {
						ct = 10 + ct - 'a';
					}
					v |= ct;
				}
				key.write[i] = v;
			}
		}
		fae.instantiate();
		if (fae.is_null()) {
			add_message(EXPORT_MESSAGE_ERROR, TTR("Save PCK"), TTR("Can't create encrypted file."));
			return ERR_CANT_CREATE;
		}
		err = fae->open_and_parse(f, key, FileAccessEncrypted::MODE_WRITE_AES256, false);
		if (err != OK) {
			add_message(EXPORT_MESSAGE_ERROR, TTR("Save PCK"), TTR("Can't open encrypted file to write."));
			return ERR_CANT_CREATE;
		}
		fhead = fae;
	}
	for (int i = 0; i < pd.file_ofs.size(); i++) {
		uint32_t string_len = pd.file_ofs[i].path_utf8.length();
		uint32_t pad = _get_pad(4, string_len);
		fhead->store_32(string_len + pad);