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

ober

5d4ad6c6e377a4dda94863b80c32e1406c156357

diff --git a/.builds/ci.yml b/.builds/ci.yml
index ec96ed6..5d7076c 100644
--- a/.builds/ci.yml
+++ b/.builds/ci.yml
@@ -32,6 +32,7 @@ tasks:
 - package: |
     cd jerboa-aws
     J="$HOME/jerboa/dist/jerboa"
+    chmod -R go-w "$HOME/.cache"
     "$J" pkg verify
     "$J" pkg policy
     "$J" pkg build