Using rtools pkgconfig

[jeroen]

I think this way of conditionally using pkg-config is both simplier and more robust, because we actually check if we can use it to get the library we need.

@kalibera does this make sense? It seems to work on rtools42 and rtools43 and rtools43-aarch.

[kalibera]

@kalibera does this make sense? It seems to work on rtools42 and rtools43 and rtools43-aarch.

I think this is a valid alternative to the check I offered, whether simpler or not is probably a matter of opinion and which to choose is up to the package maintainer. Otherwise see my comment https://github.com/rspatial/terra/pull/1306#issuecomment-1763997831

[rhijmans]

Thanks for all the help. I copied the Makevars file from "sf".