gphoto2.ds: Don't warn about libjpeg if gphoto support is not enabled.
diff --git a/dlls/gphoto2.ds/gphoto2_i.h b/dlls/gphoto2.ds/gphoto2_i.h
index 3e91d6c..bb2b6e3 100644
--- a/dlls/gphoto2.ds/gphoto2_i.h
+++ b/dlls/gphoto2.ds/gphoto2_i.h
@@ -24,7 +24,7 @@
 # error You must include config.h first
 #endif
 
-#if !defined(HAVE_JPEGLIB_H)
+#if defined(HAVE_GPHOTO2) && !defined(HAVE_JPEGLIB_H)
 # warning "gphoto2 support in twain needs jpeg development headers"
 # undef HAVE_GPHOTO2
 #endif