add default AWS region for SCCACHE

Author: wdvr

.ci/docker/common/install_cache.sh

@@ -79,6 +79,7 @@ EOF
 init_sccache() {
   # This is the remote cache bucket
   export SCCACHE_BUCKET=ossci-compiler-cache-circleci-v2
+  export SCCACHE_REGION=us-east-1
   export SCCACHE_S3_KEY_PREFIX=executorch
   export SCCACHE_IDLE_TIMEOUT=0
   export SCCACHE_ERROR_LOG=/tmp/sccache_error.log