This separates compiling platform.dill files from the patch_sdk.dart
script. The motivation for that is that I'm working on reading patch
files directly from Fasta, so we can completely remove the build step
for generating patched_sdk and dart2js_patched_sdk.
Short-term this should allow Paul to add a strong-mode version of
platform.dill without causing to many conflicts with my work on
patches.
Change-Id: I1150845b2986348d4fffe27092701d8a9b57ea54
Reviewed-on: https://dart-review.googlesource.com/11506
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Peter von der Ahé