* Remove now unnecessary portions of build.
* Add a compilePackageES5 method to build ES5 from sources
* Rework all package.json and rollup config files to new format
* Remove "extends" from tsconfig-build.json files and fixup compilation roots
PR Close#18541
Removes the tsickle dependency added when tsickle was added to the
transform compiler.
Added a test to ensure stray dependencies are not added and no
errors are introduced during module flattening.
Jason Aden
Chuck Jazdzewski
Miško Hevery