PICO_SDK_PATH variable in Makefile is confusing

[WizardUli]

The following line does not seem to have any effect https://github.com/majbthrd/DapperMime/blob/2d31d41f8225c263eefa321b08768d544ad0915b/Makefile#L4

Right now it seems one has to specify PICO_SDK_PATH as an environment variable. It is unfortunate that after doing git clone --recursive on this repo we have the SDK already downloaded but still we need to do some superfluous environment setup.