Toolchain script updates

Toolchain script updates

This set of changes brings the toolchain scripts up-to-date, now that a few fixes have been merged to stabilize the toolchain build:

- https://github.com/zerovm/glibc/pull/9
- https://github.com/zerovm/zrt/pull/91

NOTE: These changes are not quite suitable for use in the CI environment--we still need to figure out packaging for toolchain.