notmuch: install ruby bindings

previously ruby bindings were never actually installed into $out

pkgs/applications/networking/mailreaders/notmuch/default.nix

@@ -7,6 +7,7 @@
 , ruby
 , which, dtach, openssl, bash, gdb, man
 , withEmacs ? true
+, withRuby ? true
 }:
 
 stdenv.mkDerivation rec {
@@ -29,15 +30,15 @@ stdenv.mkDerivation rec {
     pythonPackages.sphinx     # (optional) documentation -> doc/INSTALL
     texinfo                   # (optional) documentation -> doc/INSTALL
     pythonPackages.cffi
-  ] ++ lib.optional withEmacs emacs;
+  ] ++ lib.optional withEmacs emacs
+    ++ lib.optional withRuby ruby;
 
   buildInputs = [
     gnupg                     # undefined dependencies
     xapian gmime talloc zlib  # dependencies described in INSTALL
     perl
     pythonPackages.python
-    ruby
-  ];
+  ] ++ lib.optional withRuby ruby;
 
   postPatch = ''
     patchShebangs configure test/
@@ -56,7 +57,7 @@ stdenv.mkDerivation rec {
     "--infodir=${placeholder "info"}/share/info"
   ] ++ lib.optional (!withEmacs) "--without-emacs"
     ++ lib.optional withEmacs "--emacslispdir=${placeholder "emacs"}/share/emacs/site-lisp"
-    ++ lib.optional (isNull ruby) "--without-ruby";
+    ++ lib.optional (!withRuby) "--without-ruby";
 
   # Notmuch doesn't use autoconf and consequently doesn't tag --bindir and
   # friends
@@ -87,6 +88,12 @@ stdenv.mkDerivation rec {
 
   postInstall = lib.optionalString withEmacs ''
     moveToOutput bin/notmuch-emacs-mua $emacs
+  '' + lib.optionalString withRuby ''
+    make -C bindings/ruby install \
+      vendordir=$out/lib/ruby \
+      SHELL=$SHELL \
+      $makeFlags "''${makeFlagsArray[@]}" \
+      $installFlags "''${installFlagsArray[@]}"
   '';
 
   passthru = {