formalize the presence of build.sh.

After discussing with yetus community we will need a build.sh for every language.
Currently it is present for a few and not for all

Busbey-MBA:avro busbey$ find . -name build.sh
./build.sh
./lang/c/build.sh
./lang/c++/build.sh
./lang/csharp/build.sh
./lang/js/build.sh
./lang/php/build.sh
./lang/ruby/build.sh

The objective of this task is to create a build.sh for each of the languages.

It might be good idea to refactor the top level build.sh to use the new build.sh scripts like it does for other languages.