Re-enable autoruns for cmd.exe on Windows

This acts as a revert of b83747a8a6 and 9886744a36.  As pointed out
by Noah, HEAD and REL_17_STABLE are in a weird state where the code
paths adding /D would limit the spawn of child processes, but we still
have code paths where the spawn of more than one child process(es) would
be possible.

Let's remove these /D switches for now, to bring back the code into a
state consistent with how autorun is configured on a Windows host.

Reported-by: Noah Misch
Discussion: https://postgr.es/m/20240630021211.f3.nmisch@google.com
Backpatch-through: 17

src/bin/pg_ctl/pg_ctl.c

@@ -552,11 +552,11 @@ start_postmaster(void)
 		else
 			close(fd);
 
-		cmd = psprintf("\"%s\" /D /C \"\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1\"",
+		cmd = psprintf("\"%s\" /C \"\"%s\" %s%s < \"%s\" >> \"%s\" 2>&1\"",
 					   comspec, exec_path, pgdata_opt, post_opts, DEVNULL, log_file);
 	}
 	else
-		cmd = psprintf("\"%s\" /D /C \"\"%s\" %s%s < \"%s\" 2>&1\"",
+		cmd = psprintf("\"%s\" /C \"\"%s\" %s%s < \"%s\" 2>&1\"",
 					   comspec, exec_path, pgdata_opt, post_opts, DEVNULL);
 
 	if (!CreateRestrictedProcess(cmd, &pi, false))

src/test/regress/pg_regress.c

@@ -1244,7 +1244,7 @@ spawn_process(const char *cmdline)
 		comspec = "CMD";
 
 	memset(&pi, 0, sizeof(pi));
-	cmdline2 = psprintf("\"%s\" /d /c \"%s\"", comspec, cmdline);
+	cmdline2 = psprintf("\"%s\" /c \"%s\"", comspec, cmdline);
 
 	if (!CreateRestrictedProcess(cmdline2, &pi))
 		exit(2);