Fix syntax for file existence check in action.yml

.github/actions/use-ccache/action.yml

@@ -36,7 +36,7 @@ runs:
         -e 's/^HOSTCC[[:space:]]*[:?+]?=.*/HOSTCC = ccache clang/' \
         -e 's/^HOSTCXX[[:space:]]*[:?+]?=.*/HOSTCXX = ccache clang++/' \
         build/kernel/_setup_env.sh
-      elif [[-f kernel/build/kernel/build.sh ]]; then
+      elif [[ -f kernel/build/kernel/build.sh ]]; then
        sed -i -E \
         -e 's/^CC[[:space:]]*[:?+]?=.*/CC = ccache clang/' \
         -e 's/^CXX[[:space:]]*[:?+]?=.*/CXX = ccache clang++/' \