Enable meta.cross for mpich related packages

pkgs/mpich/default.nix

@@ -56,5 +56,6 @@ in mpich.overrideAttrs (old: {
 
   meta = old.meta // {
     maintainers = old.meta.maintainers ++ (with lib.maintainers.bsc; [ rarias ]);
+    cross = true;
   };
 })

pkgs/osu/default.nix

@@ -44,5 +44,6 @@ stdenv.mkDerivation rec {
     homepage = "http://mvapich.cse.ohio-state.edu/benchmarks/";
     maintainers = [ ];
     platforms = lib.platforms.all;
+    cross = true;
   };
 }

pkgs/sonar/default.nix

@@ -35,5 +35,6 @@ stdenv.mkDerivation rec {
     maintainers = with lib.maintainers.bsc; [ rarias ];
     platforms = lib.platforms.linux;
     license = lib.licenses.mit;
+    cross = true;
   };
 }

pkgs/tampi/default.nix

@@ -68,5 +68,6 @@ in stdenv.mkDerivation {
     maintainers = with lib.maintainers.bsc; [ rarias ];
     platforms = lib.platforms.linux;
     license = lib.licenses.gpl3Plus;
+    cross = true;
   };
 }