2021.04.16 22:58 "Re: [Tiff] tiffcp: LERC codec options refer to zstd even if zstd support is not present", by Miguel Medalha
Check you have the #define LERC_VERSION_MAJOR in the installed Lerc_c_api.h
The libtiff build needs 'Lerc.h' and 'Lerc_c_api.h'.
Since both are together under 'lerc\src\LercLib', I took both from there. It happens that there is another 'Lerc_c_api.h' under ' lerc\include'. This is different and this is the one containing the definition you point to. Do they need to be different?
If I use the one under 'lerc\include' libtiff builds Ok.