In https://bugs.webkit.org/show_bug.cgi?id=192384 I'm adding FindNghttp2 and FindPixman to the CMake. Neither of these libraries is actually referenced within WebKit but they are dependencies when cURL and Cairo are compiled statically. It seems like the current Find* don't necessarily take pkg-config into account when returning libraries. Also pkg-config isn't as ubiquitous on Windows development machines. These things should be solvable.
You can get Windows binary from pkg-config-lite. https://sourceforge.net/projects/pkgconfiglite/