tests.pkg-configPackages: Filter out broken packages

Some packages are only marked broken on specific platforms, so we
filter those out as well.

Consequently, this might not raise an error if the attribute value
needs to point to a different pkgs attribute, but this is not something
we can detect. For now, we'll have to rely on users of such pkg-config
packages to report that kind of error.

There's really not much we can do about this here.

pkgs/test/pkg-config-packages.nix

@@ -30,6 +30,13 @@ let
       # single test, which we want to do in `passthru.tests`, or interactively.
       null
 
+    else if ! pkg?meta.broken
+    then
+      throw "pkg-config module `${escapeNixIdentifier moduleName}` does not have a `meta.broken` attribute. This can't be right. Please check the attribute value for `${escapeNixIdentifier moduleName}` in `pkgs/top-level/pkg-config.packages.nix` in Nixpkgs."
+
+    else if pkg.meta.broken
+    then null
+
     else makePkgConfigTest moduleName pkg;
 
   makePkgConfigTest = moduleName: pkg: runCommand "check-pkg-config-${moduleName}" {