8523 Fix clobber in a few Makefiles

Review Request #636 — Created July 28, 2017 and submitted — Latest diff uploaded

- CURTYPE override needs to be a $(MAKE) command-line macro def not env var
- ROOTONBLDLIBPY needs clean/clobber-conditional handling too or else an install runs upon clobber
1. A full lint build was done in the new branch, and the resulting file set was identical to that for a full lint build of the master branch.
2. An inspection of the nightly log of the build of the new branch showed that a spurious "install" was no longer run during clobber.
3. A manual run of clobber was affirmed in the new branch to remove both "library" and "standalone" artifacts vs the master branch where only "library" artifacts were removed.