bin/compile-examples.sh should do a touch on source files before compiling

bin/compile-examples.sh is used to regenerate the examples entities after modifying the compiler.
When the schemas are not modified, avro compiler don't overwrite the destination .java classes.
If we 'touch' the source files we will force the regeneration of the entities always. Just a convenience modification.

(I noticed now a typo in that script. In line 41 must be used the command goracompiler)