generate-cross-file.py does not add arch specific pkg-config directory

[varbanv]

It looks like on debian buster (arm64), there are a lot of configs installed under usr/lib/aarch64-linux-gnu/pkgconfig and generate-cross-file.py does not include that in the pkg_config_libdir variable for the meson cross-compile config.

[dabrain34]

Hello,

Thanks for your feedback. Feel free to open a PR to address this issue.