Use pkg-config on Windows when available.

[kalibera]

This will use pkg-config to establish the libraries to link when pkg-config is available (which will soon be in Rtools). This should reduce the frequency of needed updates to linking when new features are linked/enabled in gdal.

[kadyb]

@edzer, it may be worth waiting until the Rtools will be update, because GHA and R-Universe will stop working (see: rspatial/terra#1306).

[kalibera]

Updated Rtools with pkg-config are already available at https://cran.r-project.org/bin/windows/Rtools/rtools43/rtools.html
Depending on which make your github actions use, you however may have to create a pkg-config.bat wrapper - more in https://cran.r-project.org/bin/windows/base/howto-R-devel.html, "Establishing the linking order in R packages via pkg-config". But, certainly, this is not urgent.

[edzer]

@kalibera would merging this prevent the error we now see on r-devel-windows?

[kalibera]

@kalibera would merging this prevent the error we now see on r-devel-windows?

Yes

[edzer]

Thanks!