Leif suggested we move away from using recursive make to improve the parallel
build. I’ve posted a pull request
<https://github.com/apache/trafficserver/pull/1115> to show what this could
look like. In most cases, we would need to use per-target compiler flags, or
radically simplify the set of compiler options we use. With a single global
make we would not be able to use AM_CXXFLAGS as much.
An alternative approach to this PR would be to carve out 2 or 3 large chunks of
the build into a recursive make (maybe cmd, plugins, and core), then be
non-recursive in each chunk.