windows: allow MrEd-based console apps and Mz-based consoleless apps

svn: r230

collects/compiler/private/winsubsys.ss

@@ -0,0 +1,19 @@
+(module winsubsys mzscheme
+  (provide set-subsystem)
+  
+  (define DF_NewHeaderOffset #x3C)
+  (define DF_SubsystemOffset #x5C)
+  
+  (define (set-subsystem file subsys)
+    (let-values ([(in out) (open-input-output-file file 'update)])
+      (file-position in DF_NewHeaderOffset)
+      (let ([offset (integer-bytes->integer (read-bytes 4 in) #f #f)])
+        (file-position out (+ offset DF_SubsystemOffset))
+        (write-bytes (integer->integer-bytes
+                      (case subsys
+                        [(windows) 2]
+                        [(console) 3])
+                      4 #f #f)
+                     out)
+        (close-input-port in)
+        (close-output-port out)))))