libc/uClibc: remove use of snapshots and specific date

We now have the ability to use a custom location, so supporting
snapshots or custom date is no longer needed. Let the user do the
required preparation in this case.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

reporter_name="Dragan Marinkovic <marinkovic.dragan@gmail.com>"

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