added error message if ./st-flash not found in root dir
added error message if ./st-flash not found in root dir

JuliusKunze/kotlin-native,jiaminglu/kotlin-native,olonho/carkot,JuliusKunze/kotlin-native,jiaminglu/kotlin-native,jiaminglu/kotlin-native,JuliusKunze/kotlin-native,wiltonlazary/kotlin-native,olonho/carkot,olonho/carkot,olonho/carkot,JetBrains/kotlin-native,JetBrains/kotlin-native,jiaminglu/kotlin-native,JetBrains/kotlin-native,jiaminglu/kotlin-native,JuliusKunze/kotlin-native,jiaminglu/kotlin-native,wiltonlazary/kotlin-native,JetBrains/kotlin-native,jiaminglu/kotlin-native,JuliusKunze/kotlin-native,olonho/carkot,wiltonlazary/kotlin-native,JetBrains/kotlin-native,jiaminglu/kotlin-native,JuliusKunze/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,JuliusKunze/kotlin-native,JuliusKunze/kotlin-native,JetBrains/kotlin-native,JetBrains/kotlin-native,wiltonlazary/kotlin-native,olonho/carkot,olonho/carkot,JetBrains/kotlin-native