Depending on architecture, perlasm differed on which one or both of:

  perl foo.pl flavor output.S
  perl foo.pl flavor > output.S

Upstream has now unified on the first form after making a number of
changes to their files (the second does not even work for their x86
files anymore). Sync those portions of our perlasm scripts with upstream
and update CMakeLists.txt and generate_build_files.py per the new
convention.

This imports various commits like this one:
184bc45f68 (this was done by taking a
diff, so I don't have the full list)

Confirmed that generate_build_files.py sees no change.

BUG=14

Change-Id: Id2fb5b8bc2a7369d077221b5df9a6947d41f50d2
Reviewed-on: https://boringssl-review.googlesource.com/8518
Reviewed-by: Adam Langley <agl@google.com>