findunref build shouldn't fail if SCM can't be determined
tools - gate/build tools
usr/src/tools/findunref/Makefile deals with the possibility SCM_TYPE is "none", but not the possibility that it's "unknown", which in some cases it may be (when using bldenv, for instance).
- It should deal with either possibility in the same way
- bldenv should use "none" the same as nightly does