ci: set umask 022 to prevent group-writable cache dirs (sr.ht default umask creates 0775 dirs)

ober

85fdf8d980c0588772d1b5effe52d598b713ab8d

diff --git a/.builds/ci.yml b/.builds/ci.yml
index 59fb25d..940b244 100644
--- a/.builds/ci.yml
+++ b/.builds/ci.yml
@@ -21,6 +21,7 @@ artifacts:
 - jerboa-aws/jerboa-aws-0.1.0.jpkg
 tasks:
 - build-jerboa: |
+    umask 022
     cd jerboa
     sudo fallocate -l 4G /swapfile && sudo chmod 600 /swapfile && sudo mkswap /swapfile && sudo swapon /swapfile
     export CARGO_BUILD_JOBS=1