ci: chmod go-w ~/.cache before pkg commands (sr.ht cache is group-writable)

ober

d1363d5314d1519edb4590d031af3119b8fe5385

diff --git a/.builds/ci.yml b/.builds/ci.yml
index 4730f76..e6cb1c2 100644
--- a/.builds/ci.yml
+++ b/.builds/ci.yml
@@ -33,6 +33,7 @@ tasks:
 - package: |
     cd jerboa-drive
     J="$HOME/jerboa/dist/jerboa"
+    chmod -R go-w "$HOME/.cache"
     "$J" pkg verify
     "$J" pkg policy
     "$J" pkg build