[lld-macho][nfc] Sort OutputSections based on explicit order of command-line inputs

This diff paves the way for {D102964} which adds a new kind of
InputSection.

We previously maintained section ordering implicitly: we created
InputSections as we parsed each file in command-line order, and passed
on this ordering when we created OutputSections and OutputSegments by
iterating over these InputSections. The implicitness of the ordering
made it difficult to refactor the code to e.g. handle a new type of
InputSection. As such, I've codified the ordering explicitly via
`inputOrder` fields. This also allows us to use `sort` instead of
`stable_sort`.

Benchmarking chromium_framework on my 3.2 GHz 16-Core Intel Xeon W:

      N           Min           Max        Median           Avg        Stddev
  x  20          4.23          4.35          4.27         4.274   0.030157481
  +  20          4.24          4.38          4.27        4.2815   0.033759989
  No difference proven at 95.0% confidence

Reviewed By: #lld-macho, alexshap

Differential Revision: https://reviews.llvm.org/D102972

0 files changed, 0 insertions, 0 deletions