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

ober

10b229dddfadfc5de850e03f082935b8a9fa1a29

diff --git a/.builds/ci.yml b/.builds/ci.yml
index 9de9b33..d87a774 100644
--- a/.builds/ci.yml
+++ b/.builds/ci.yml
@@ -32,6 +32,7 @@ tasks:
 - package: |
     cd jerboa-proton-bridge
     J="$HOME/jerboa/dist/jerboa"
+    chmod -R go-w "$HOME/.cache"
     "$J" pkg verify
     "$J" pkg policy
     "$J" pkg build