ci: add JERBOA_CC_OPT=-O0 (OOM fix) and mkdir -p ~/.cache

ober

1da7bfe94d906986b40b95d03d7cb3bbcf12e1b7

diff --git a/.build.yml b/.build.yml
index 90c2701..98630b7 100644
--- a/.build.yml
+++ b/.build.yml
@@ -69,7 +69,7 @@ tasks:
   - package: |
       cd jerboa-browser
       J="$HOME/jerboa/bin/jerboa"
-      SCHEME="$(command -v scheme)" chmod -R go-w "$HOME/.cache"
+      mkdir -p "$HOME/.cache" && chmod -R go-w "$HOME/.cache"
       "$J" pkg verify
       SCHEME="$(command -v scheme)" "$J" pkg policy
       SCHEME="$(command -v scheme)" "$J" pkg build