firefox wrapper: fix merging of policies files

If multiple extraPolicies or extraPoliciesFiles are given, the JSON
objects are merged using `jq` with the `a + b` operator, which simply
combines all the unique keys of `a`, `b` with the duplicated keys from
`b`, without recursion.
This strategy is completely wrong in this case: as policy files consists
of a single key, "policies", all that happens is that `b` takes over, in
other words:

    $(jq -s '.[0] + .[1]' a b) == $(cat b)

So there is no merging at all, the final policies.json file is simply
the last file in the list.

The `a * b` operation should be used instead, which performs the merge
by recursing in each key.

1 files changed, 1 insertions, 1 deletions

diff --git a/pkgs/applications/networking/browsers/firefox/wrapper.nix b/pkgs/applications/networking/browsers/firefox/wrapper.nix
index e909b15f77a..12924180c25 100644
--- a/pkgs/applications/networking/browsers/firefox/wrapper.nix
+++ b/pkgs/applications/networking/browsers/firefox/wrapper.nix
@@ -362,7 +362,7 @@ let
 
         extraPoliciesFiles=(${builtins.toString extraPoliciesFiles})
         for extraPoliciesFile in "''${extraPoliciesFiles[@]}"; do
-          jq -s '.[0] + .[1]' "$POL_PATH" $extraPoliciesFile > .tmp.json
+          jq -s '.[0] * .[1]' "$POL_PATH" $extraPoliciesFile > .tmp.json
           mv .tmp.json "$POL_PATH"
         done