Fix Parallel Compilation

This patch does two things:

1. it broadens the interface for the compiler module so that
   non-first-file modules can possibly be parallelized. This is done by
   dynamically switching on `[ListOfFiles]`, which remains sequential as
   before, or `{[SeqPriority], [Parallel]}`, which divides regular files
   between higher priority ones and those that can be in parallel
2. implements this mechanism in the rebar compiler, based on the erl
   file digraph. If a file has an in-neighbour, it is depended on by
   another file. The mechanism therefore makes it so all files that have
   dependants get compiled in their strict relative sequential order
   first, and then the undepended-on files get compiled together in
   parallel.

By running:

  ./rebar3 ct --suite test/rebar_compile_SUITE.erl --case \
  recompile_when_parse_transform_inline_changes --repeat 50

the previous iteration of this would rapidly fail, and this one succeeds
every time.

0 files changed, 0 insertions, 0 deletions