cmake: put the Perl modules into the correct location again

cmake: put the Perl modules into the correct location again

In ccfba9e0c45 (Makefile: use "generate-perl.sh" to massage Perl
library, 2024-12-06), the previous strategy (which avoided spawning a
shell script to transform the files) was replaced by the same
`generate-perl.sh` invocation as for the Makefile-based build.

The only difference is that now the transformation tries to handle the
Perl modules in-place (which ends up in empty files because the same
file is used as input and output via stdin/stdout redirection), and the
Perl script cannot find them anymore because they are not in the
expected place.

Let's put them into the expected place again, i.e. into
`perl/build/lib/` instead of `perl/`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>