Integrated NaCL in the build process of Spark

Depends on: https://github.com/dart-lang/spark/pull/1478

Fixed #1480
Fixed #1356

Relevant commits to look at:
https://github.com/dinhviethoa/spark/commit/6a7bb672da72d4d1b041da7c9d998f2622cd23b8
https://github.com/dinhviethoa/spark/commit/9a4b936aac8060e9284556b15888c99b78378f3b
https://github.com/dinhviethoa/spark/commit/db8352edb6f17b62464a64abf97c39b6956a54ea

review: @devoncarew