propagate enable-check-prelex-flags to separate-eval sub-process in tests

original commit: 760c3414e412ecb6708c890e32fdb8056be1e805

LOG

@@ -937,3 +937,5 @@
     wininstall/product.wxs
 - Use Windows path separator character when finding boot files on Windows.
     scheme.c
+- Propagate enable-check-prelex-flags to separate-eval sub-process in tests.
+    mats.ss

mats/mat.ss

@@ -380,6 +380,7 @@
                   (open-process-ports (format "~a -q" (patch-exec-path *scheme*))
                     (buffer-mode block)
                     (native-transcoder))])
+      (pretty-print `(#%$enable-check-prelex-flags ,(#%$enable-check-prelex-flags)) to-stdin)
       (for-each (lambda (expr) (pretty-print expr to-stdin)) expr*)
       (close-port to-stdin)
       (let* ([stdout-stuff (slurp from-stdout)]