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>

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