pgsql: pg_regress: Disable autoruns for cmd.exe on Windows

pg_regress: Disable autoruns for cmd.exe on Windows

This is similar to 9886744a361b, to prevent the execution of other
programs due to autorun configurations which could influence the
postmaster startup.

This was originally applied on HEAD as of 83c75ac7fb69 without a
backpatch, but the patch has survived CI and buildfarm cycles.  I have
checked that cmd /d exists down to Windows XP, which should make this
change work correctly in the oldest branches still supported.

Discussion: https://postgr.es/m/20230922.161551.320043332510268554.horikyota.ntt@gmail.com
Backpatch-through: 12

Branch
------
REL_15_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/7e7d827f57b982f1c68ef5852a2c16a6be28cc33

Modified Files
--------------
src/test/regress/pg_regress.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)