pgsql: meson: Fix import library name in Windows

meson: Fix import library name in Windows

This changes the import library name from 'postgres.exe.lib' to
'postgres.lib', which is what it was with the old MSVC build system.
Extension builds use that name.

Bug: #18513
Reported-by: Muralikrishna Bandaru <muralikrishna.bandaru@enterprisedb.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/c61c0cb3a99285db36806b592bd8c540c98757e5

Modified Files
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meson.build             | 6 +++---
src/backend/meson.build | 2 +-
2 files changed, 4 insertions(+), 4 deletions(-)