systems: fix lib-tests

These were broken by the added system doubles. This just adds those to
the lib-tests.

lib/systems/doubles.nix

@@ -57,5 +57,7 @@ in rec {
   wasi    = filterDoubles predicates.isWasi;
   windows = filterDoubles predicates.isWindows;
 
+  embedded = filterDoubles predicates.isNone;
+
   mesaPlatforms = ["i686-linux" "x86_64-linux" "x86_64-darwin" "armv5tel-linux" "armv6l-linux" "armv7l-linux" "armv7a-linux" "aarch64-linux" "powerpc64le-linux"];
 }

lib/systems/inspect.nix

@@ -44,6 +44,7 @@ rec {
     isCygwin       = { kernel = kernels.windows; abi = abis.cygnus; };
     isMinGW        = { kernel = kernels.windows; abi = abis.gnu; };
     isWasi         = { kernel = kernels.wasi; };
+    isNone         = { kernel = kernels.none; };
 
     isAndroid      = [ { abi = abis.android; } { abi = abis.androideabi; } ];
     isMusl         = with abis; map (a: { abi = a; }) [ musl musleabi musleabihf ];