Update cmd.sh user_version.h sed command

in light of changes made as part of
nodemcu/nodemcu-firmware#2269

cmd.sh

@@ -57,7 +57,7 @@ cd /opt/nodemcu-firmware
 # EXTRA_CCFLAGS="-DBUILD_DATE=... AND -DNODE_VERSION=..." to make turned into an escaping/expanding nightmare for which
 # I never found a good solution
 if [ "$CAN_MODIFY_VERSION" = true ]; then
-  sed -i 's/\(NodeMCU [^"]*\)/\1 built with Docker provided by frightanic.com\\n\\tbranch: '"$BRANCH"'\\n\\tcommit: '"$COMMIT_ID"'\\n\\tSSL: '"$SSL"'\\n/g' app/include/user_version.h
+  sed -i '/#define NODE_VERSION[[:space:]]/ s/$/ " built with Docker provided by frightanic.com\\n\\tbranch: '"$BRANCH"'\\n\\tcommit: '"$COMMIT_ID"'\\n\\tSSL: '"$SSL"'\\n"/g' app/include/user_version.h
   sed -i 's/"unspecified"/"created on '"$BUILD_DATE"'\\n"/g' app/include/user_version.h
 fi