ci(build): allow cache save to push tag/release (contents: read -> write)

Cache-save pushes ccache-cache/bazel-cache tags and uploads via gh release
upload; read-only perms caused instant 403 and 1.3s retry failures. Aligns
with OnePlus workflow which uses contents: write

Co-Authored-By: internal-model

.github/workflows/build.yml

@@ -1,6 +1,6 @@
 name: Kernel Build Process
 permissions:
-  contents: read
+  contents: write
   actions: write
 
 on: