Meson default pkgconfig directory on FreeBSD

[Frédéric Fauberteau <triaxx%NetBSD.org@localhost>]

I get the following error when trying to install graphics/gdk-pixbuf2 on FreeBSD.

=> Generating post-install file lists
pkg_create: can't stat `/var/cache/pkgsrc/work/graphics/gdk-pixbuf2/work/.destdir/usr/pkg/lib/pkgconfig/gdk-pixbuf-2.0.pc'
=> Checking file-check results for gdk-pixbuf2-2.40.0nb1
ERROR: ************************************************************
ERROR: The following files are in the PLIST but not in /var/cache/pkgsrc/work/graphics/gdk-pixbuf2/work/.destdir/usr/pkg:
ERROR:         /var/cache/pkgsrc/work/graphics/gdk-pixbuf2/work/.destdir/usr/pkg/lib/pkgconfig/gdk-pixbuf-2.0.pc
ERROR: ************************************************************
ERROR: The following files are in /var/cache/pkgsrc/work/graphics/gdk-pixbuf2/work/.destdir/usr/pkg but not in the PLIST:
ERROR:         /var/cache/pkgsrc/work/graphics/gdk-pixbuf2/work/.destdir/usr/pkg/libdata/pkgconfig/gdk-pixbuf-2.0.pc
*** Error code 1

It seems that meson changes the default pkgconfig directory to $(PREFIX)/libdata/pkgconfig: https://github.com/mesonbuild/meson/pull/4410

Surprisingly, devel/glib2 that uses meson too seems to be not affected.