Fix offline cache of .uf2 files (#3997)
Fix offline cache of .uf2 files (#3997)


Microsoft/pxt,Microsoft/pxt,playi/pxt,switch-education/pxt,playi/pxt,switch-education/pxt,switch-education/pxt,switch-education/pxt,switchinnovations/pxt,Microsoft/pxt,Microsoft/pxt,switchinnovations/pxt,Microsoft/pxt,playi/pxt,switch-education/pxt,switchinnovations/pxt,playi/pxt,switchinnovations/pxt