Only show/build a package on the platforms listed in meta.platforms

The function ‘mkDerivation’ now checks whether the current platform
type is included in a package's meta.platform field.  If not, it
throws an exception:

  $ nix-build -A linux --argstr system x86_64-darwin
  error: user-thrown exception: the package ‘linux-3.10.15’ is not supported on ‘x86_64-darwin’

These packages also no longer show up in ‘nix-env -qa’ output.  This
means, for instance, that the number of packages shown on
x86_64-freebsd has dropped from 9268 to 4764.

Since meta.platforms was also used to prevent Hydra from building some
packages, there now is a new attribute meta.hydraPlatforms listing the
platforms on which Hydra should build the package (which defaults to
meta.platforms).

pkgs/os-specific/linux/nvidia-x11/default.nix

@@ -21,8 +21,7 @@ stdenv.mkDerivation {
 
   patches =
     [ ./version-test.patch ]
-    ++ optional (!libsOnly && versionAtLeast kernelDev.version "3.11") ./nvidia-drivers-linux-3.11-incremental.patch
-    ;
+    ++ optional (!libsOnly && versionAtLeast kernelDev.version "3.11") ./nvidia-drivers-linux-3.11-incremental.patch;
 
   src =
     if stdenv.system == "i686-linux" then
@@ -58,5 +57,7 @@ stdenv.mkDerivation {
     homepage = http://www.nvidia.com/object/unix.html;
     description = "X.org driver and kernel module for NVIDIA graphics cards";
     license = stdenv.lib.licenses.unfreeRedistributable;
+    platforms = stdenv.lib.platforms.linux;
+    hydraPlatforms = [];
   };
 }