Commit
f06b1c598 removed validate_exec from pg_upgrade and instead
exported it from src/common, but the macro for checking executable
suffix on Windows was accidentally left. Fix by removing.
Author: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://postgr.es/m/
c1d63754-cb85-2d8a-8409-
bde2c4d2d04b@gmail.com