Didn't backport the new URL scheme when we updated the toolchain version. Have put a link on the server so in this case the "osx" toolchain URL remains valid. Closes https://github.com/espressif/esp-idf/issues/5720
Closes https://github.com/espressif/esp-idf/issues/503 Closes https://github.com/espressif/esp-idf/issues/2607