pgsql: Fix searchpath for modern Perl for genbki.pl

Fix searchpath for modern Perl for genbki.pl

This was fixed for MSVC tools by commit 1df92eeafefac4, but per
buildfarm member bowerbird genbki.pl needs the same treatment.

Backpatch to all live branches.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f884a96819ad375a3220fffadcd47d0dcabeece4

Modified Files
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src/backend/catalog/genbki.pl | 4 ++++
1 file changed, 4 insertions(+)