Jonah Williams c18e45dca7 generate package config during runhooks (flutter/engine#19428)
The dart SDK needs to ship several packages which have opted into null safety for the tech preview. This requires the use of a package_config.json for compilation as this file contains the language versions. Use a dart script to generate the package_config file from the .packages file, and include that in the DEPS hooks section.

Fixes flutter/flutter#60628
2020-06-30 17:48:36 -07:00
Languages
Dart 75%
C++ 16.5%
Objective-C++ 2.9%
Java 2.8%
Objective-C 0.7%
Other 1.9%