package/libgdiplus: add upstream link to patch

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Arnout Vandecappelle <arnout@mind.be>
(cherry picked from commit 200b264b7a12c582a5d200d02fec8d9babd79651)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/libgdiplus/0001-Build-unit-tests-only-when-enable-unit-tests-is-pass.patch

@@ -10,6 +10,7 @@ So let's disable the build of unit tests by default and introduce
 --enable-unit-tests configure option to enable it.
 
 Signed-off-by: Sergio Prado <sergio.prado@e-labworks.com>
+Upstream: https://github.com/mono/libgdiplus/pull/701
 ---
  Makefile.am  | 8 ++++++--
  configure.ac | 4 ++++