[SR-1249] [llbuild] problem in the ordering of dependencies

[aciidgh]

Previous ID	SR-1249
Radar	None
Original Reporter	@aciidb0mb3r
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	llbuild
Labels	Bug
Assignee	@ddunbar
Priority	Medium

md5: 43fa413a2e3602ffae1046b4868e6e17

Issue Description:

Discovered in #20
the order of deps should probably be maintained.

[ddunbar]

This probably isn't critical to any of the current clients, who don't actually use the order particularly much (still would be nice for deterministic behavior, though).

However, this is critical once we get to fancier clients that do things like get the contents of a directory, then discover additional dependencies on it as they progress. If we reorder those dependencies, we might compute the wrong function (from the functional view of the Core engine).