Add the ability to check if a property is present

This adds (to the ModuleContext) a facility to check if a property is
defined in a module in a Blueprints file.

Change-Id: I16a35fd236717d8797f15093c019f7cc1049fb3c
1 file changed
tree: d9a7a4ddd4ba13e6265b44acfec4a841f91d58ef
  1. blueprint/
  2. Blueprints
  3. bootstrap.bash
  4. build.ninja.in