Fix missing function in install script

etc/mongocxx/install_mongocxx.sh

@@ -12,6 +12,9 @@ fi
 
 
 # Stolen from mycroft-core/dev_setup.sh  // Rainer Kartmann
+function found_exe() {
+    hash "$1" 2>/dev/null
+}
 
 # If tput is available and can handle multiple colors
 if found_exe tput ; then