Update to latest libgit2 master

ianhattendorf · ianhattendorf · commit 80698b434aa9 · 2020-01-13T14:03:00.000-07:00
diff --git a/vendor/libgit2 b/vendor/libgit2
@@ -1 +1 @@
-Subproject commit 7b4b1930f12fac1c6ef16cd32946a46eb8eeaa5f
+Subproject commit b36f257ff380d14d6e11e6203c48659e6b921e5b
