chore: change mode of tmp cache mount

Author: rjaegers

.devcontainer/cpp/Dockerfile

@@ -42,7 +42,7 @@ RUN --mount=type=bind,source=.devcontainer/cpp/apt-requirements-clang.json,targe
     --mount=type=cache,target=/var/cache/apt,sharing=locked \
     --mount=type=cache,target=/var/lib/apt,sharing=locked \
     --mount=type=cache,target=/var/log,sharing=locked \
-    --mount=type=cache,target=/tmp,sharing=locked \
+    --mount=type=cache,target=/tmp,sharing=locked,mode=1777 \
  wget -qO - https://apt.llvm.org/llvm-snapshot.gpg.key | gpg --dearmor -o /usr/share/keyrings/llvm-snapshot-keyring.gpg \
  && wget -qO - https://dl.cloudsmith.io/public/mull-project/mull-stable/gpg.41DB35380DE6BD6F.key | gpg --dearmor -o /usr/share/keyrings/mull-project-mull-stable-archive-keyring.gpg \
  && UBUNTU_CODENAME=$(grep '^UBUNTU_CODENAME=' /etc/os-release | cut -d= -f2) \