Avoid kernel too old error when building ROS

scripts/build

@@ -1,6 +1,21 @@
 #!/bin/bash
 set -e
 
+version_gt() {
+    test "$(printf '%s\n' "$@" | sort -V | head -n 1)" != "$1";
+}
+
+
+if [ "$KERNEL_CHECK" != "0" ]; then
+    echo "Host Kernel: $(uname -r)"
+    echo "RancherOS Kernel: $KERNEL_VERSION"
+
+    if ! version_gt $(uname -r) $KERNEL_VERSION; then
+        echo "Your host kernel must be greater than RancherOS KERNEL_VERSION"
+        exit 1
+    fi
+fi
+
 echo -------------------------./build-target
 $(dirname $0)/build-target
 echo -------------------------./build-host