ci: fix sccache cache mode

Author: Itsusinn

.cross/Dockerfile

@@ -15,4 +15,4 @@ ENV CC=clang \
     CXX=clang++ \
     AR=llvm-ar \
     RUSTC_WRAPPER="/usr/bin/sccache" \
-    SCCACHE_DIRECT=true
+    SCCACHE_DIR="/tmp/sccache"

Cross.toml

@@ -1,5 +1,6 @@
 [build.env]
-passthrough = ["RUSTFLAGS", "RUSTC_BOOTSTRAP", "SCCACHE_GHA_ENABLED", "ACTIONS_RESULTS_URL", "ACTIONS_RUNTIME_TOKEN"]
+passthrough = ["RUSTFLAGS", "RUSTC_BOOTSTRAP", "SCCACHE_GHA_ENABLED"]
+volumes = ["/tmp/sccache=/tmp/sccache"]
 
 # Use clang as the C/C++ compiler to avoid the aws-lc-sys GCC memcmp bug
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95189