nrfutil: guard nrfutil-completion as optional on all platforms

nrfutil-completion is absent from source.nix on some platforms
(e.g. aarch64-linux). Unconditionally listing it in the packages
map causes an evaluation error ('attribute nrfutil-completion
missing') on those platforms.

Guard the package with lib.optional and the postBuild shell
completion installation with lib.optionalString, both keyed on
'platformSources.packages ? nrfutil-completion', so the build
succeeds on every supported platform.

Signed-off-by: Sirio Balmelli <sirio@b-ad.ch>

Author: siriobalmelli

pkgs/by-name/nr/nrfutil/package.nix

@@ -98,8 +98,8 @@ let
       (
         [
           "nrfutil"
-          "nrfutil-completion"
         ]
+        ++ lib.optional (platformSources.packages ? nrfutil-completion) "nrfutil-completion"
         ++ extensions
       );
 
@@ -151,9 +151,11 @@ symlinkJoin {
     ''
       wrapProgram "$out"/bin/nrfutil ${wrapProgramArgs}
 
-      installShellCompletion --cmd nrfutil \
-        --bash $(realpath "$out"/share/nrfutil-completion/scripts/bash/setup.bash) \
-        --zsh $(realpath "$out"/share/nrfutil-completion/scripts/zsh/_nrfutil)
+      ${lib.optionalString (platformSources.packages ? nrfutil-completion) ''
+        installShellCompletion --cmd nrfutil \
+          --bash $(realpath "$out"/share/nrfutil-completion/scripts/bash/setup.bash) \
+          --zsh $(realpath "$out"/share/nrfutil-completion/scripts/zsh/_nrfutil)
+      ''}
     '';
 
   passthru =