libffi: doCheck optionally and do so for glib-tested

This is kind-of reverting fcf99efcd.

pkgs/development/libraries/libffi/default.nix

@@ -1,4 +1,4 @@
-{ fetchurl, stdenv }:
+{ fetchurl, stdenv, dejagnu, doCheck ? false }:
 
 stdenv.mkDerivation rec {
   name = "libffi-3.2.1";
@@ -10,11 +10,15 @@ stdenv.mkDerivation rec {
 
   patches = if stdenv.isCygwin then [ ./3.2.1-cygwin.patch ] else null;
 
+  buildInputs = stdenv.lib.optional doCheck dejagnu;
+
   configureFlags = [
     "--with-gcc-arch=generic" # no detection of -march= or -mtune=
     "--enable-pax_emutramp"
   ];
 
+  inherit doCheck;
+
   dontStrip = stdenv ? cross; # Don't run the native `strip' when cross-compiling.
 
   # Install headers in the right place.

pkgs/top-level/all-packages.nix

@@ -6659,7 +6659,10 @@ let
   };
 
   glib = callPackage ../development/libraries/glib { };
-  glib-tested = glib.override { doCheck = true; }; # checked version separate to break cycles
+  glib-tested = glib.override { # checked version separate to break cycles
+    doCheck = true;
+    libffi = libffi.override { doCheck = true; };
+  };
   glibmm = callPackage ../development/libraries/glibmm { };
 
   glib_networking = callPackage ../development/libraries/glib-networking {};