Disable command echo in pg_upgrade-created windows scripts

This makes them more like the Unix equivalents.

Discussion: https://postgr.es/m/73deed30-3363-44e9-48a5-98aa66a8a00f@dunslane.net

Author: adunstan

src/bin/pg_upgrade/pg_upgrade.h

@@ -77,8 +77,9 @@ extern char *output_files[];
 #define pg_mv_file			pgrename
 #define PATH_SEPARATOR		'\\'
 #define PATH_QUOTE	'"'
-#define RM_CMD				"DEL /q"
-#define RMDIR_CMD			"RMDIR /s/q"
+/* @ prefix disables command echo in .bat files */
+#define RM_CMD				"@DEL /q"
+#define RMDIR_CMD			"@RMDIR /s/q"
 #define SCRIPT_PREFIX		""
 #define SCRIPT_EXT			"bat"
 #define EXE_EXT				".exe"