Fixes to cabal wrapper script.

The new --with-strip=... option is to prevent linking errors of the form
"Unsupported ELF machine number 0". These errors did not occur when building
and installing with cabal-install but, rather, later when linking an executable
or library that depended on the library that had been installed.

Also, replaced /usr/bin/cabal with $NEW_CABAL we cant to use a cabal-install of same version where as /usr/bin/cabal almost certainly isn't.