cs: fix -C flag to set (system-type 'cross)

racket/src/cs/main.sps

@@ -385,6 +385,7 @@
              [("-C" "--cross")
               (set! host-config-dir init-config-dir)
               (set! host-collects-dir init-collects-dir)
+              (set-cross-mode! 'force)
               (loop (cdr args))]
              [("-U" "--no-user-path")
               (set! user-specific-search-paths? #f)

racket/src/cs/rumble.sls

@@ -478,6 +478,7 @@
           system-path-convention-type
           system-library-subpath-string ; not exported to Racket
           set-get-machine-info!         ; not exported to Racket
+          set-cross-mode!               ; not exported to Racket
 
           unsafe-car
           unsafe-cdr

racket/src/cs/rumble/system.ss

@@ -11,6 +11,9 @@
    [(getenv "PLT_CS_MAKE_UNIX_STYLE_MACOS") #t]
    [else #f]))
 
+(define cross-mode 'infer)
+(define (set-cross-mode! m) (set! cross-mode m))
+
 (define (system-type* mode)
   (case mode
     [(vm) 'chez-scheme]
@@ -29,7 +32,7 @@
                    [else (string->utf8 ".so")])]
     [(so-mode) 'local]
     [(fs-change) '#(#f #f #f #f)]
-    [(cross) 'infer]
+    [(cross) cross-mode]
     [else (raise-argument-error 'system-type
                                 (string-append
                                  "(or/c 'os 'word 'vm 'gc 'link 'machine\n"