fix File::open() when opening for writing

src/core/File.cc

@@ -19,8 +19,16 @@
  */
 bool File::open(const char * filename, bool writing)
 {
-    int flags = (writing ? 0 : O_RDONLY) | JES_O_BINARY;
-    int fd = ::open(filename, flags);
+    int fd;
+    if (writing)
+    {
+        /* TODO: handle mode */
+        fd = ::open(filename, O_WRONLY | O_CREAT | O_TRUNC | JES_O_BINARY, 0644);
+    }
+    else
+    {
+        fd = ::open(filename, O_RDONLY | JES_O_BINARY);
+    }
     if (fd < 0)
     {
         return false;