build fails: "PROJ.4 library not found!"

[ianxo]

Hi,
since I had quite a hard time getting XyGrib to build and run, I thought I share my problems and solutions.

As it seems, proj_api.h was remove in PROJ 8.0 and FindPROJ4.cmake is searching for said file...
My solution was to grep PROJ 7.2.1, build it and then install XyGrib via pkg manager of your liking. (e.g. yay)

I also had to copy cp /usr/local/lib/libproj.so.19 /usr/lib/
but that might be due to my installation process.

I only tested on a current Arch build :/

[gdt]

See #289 and #313, and also #200. Given those, I see this as a dup and suggest you close it.