COMP: Incremental Compilation

Modified build such that when re-building, it will
only build the affected objects/libraries or executables
instead of building everything again.

From: George Zagaris <george.zagaris@kitware.com>

git-svn-id: https://svn.alcf.anl.gov/repos/DarkUniverse/hacc/trunk/cosmotools@1968 952bdfbe-fa2e-45c0-a9ae-ac90d4a62daf
Merge branch 'svn/trunk'
ENH: Remove old & not needed  mergertree code