Add explicit dependency on mklittlefs. (#9708)

This fixes builds in very clean environment with default build target (e.g.
-t buildfs *not* explicitly specified).

Tested: pio run -e heltec-v3

Fixes #9035

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

variants/esp32/esp32-common.ini

@@ -6,6 +6,9 @@ custom_mtjson_part =
 platform =
   # renovate: datasource=custom.pio depName=platformio/espressif32 packageName=platformio/platform/espressif32
   platformio/espressif32@6.13.0
+platform_packages =
+  # renovate: datasource=custom.pio depName=platformio/tool-mklittlefs packageName=platformio/tool/tool-mklittlefs
+  platformio/tool-mklittlefs@^1.203.210628
 
 extra_scripts =
   ${env.extra_scripts}