libc/eglibc: fix installed scripts

Like rev 2002, eglibc installs some bash scripts, but use the path to the
buildtool bash as the interpreter (on the shebang line). This is only a
symlink to the real bash, and thus is not available at runtime.

Fix that by assuming that shell on the target *will* be /bin/bash.

Signed-off-by: Bryan Hundven <bryanhundven@gmail.com>
(transplanted from 6884dcb80121ebc8ce17deee62716ed75fc29393)

 # Compute IA-64-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}"

 }