internals: properly remove all docs

Part of the installed doc was not removed (if configured to).

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>
(transplanted from cb0f625b3f9f704140aaeed024baac05e6b27df0)

# Compute IA-64-specific values

CT_DoArchTupleValues() {

    # The architecture part of the tuple:

    CT_TARGET_ARCH="${CT_ARCH}"

}