Merge pull request #141072 from r-burns/validatepkgconfig-cross

[staging] validatePkgConfig: fix cross-compilation

pkgs/build-support/setup-hooks/validate-pkg-config.sh

···
     for pc in $(find "$prefix" -name '*.pc'); do
         # Do not fail immediately. It's nice to see all errors when
         # there are multiple pkgconfig files.
-        if ! pkg-config --validate "$pc"; then
+        if ! $PKG_CONFIG --validate "$pc"; then
             bail=1
         fi
     done