Update Buck

This version makes test coverage tool JaCoCo work in the wild [1].

[1] https://github.com/facebook/buck/commit/ab0133d57643925564ee208845dc8568b26b6a2c

Change-Id: I497bd5e5a88bdda1ea6b3766d199d62cb73318ed
diff --git a/.buckversion b/.buckversion
index 187f479..cff4f0f 100644
--- a/.buckversion
+++ b/.buckversion
@@ -1 +1 @@
-e42f4f1395e32a8b2e3a3ddf848e178b8558e1e9
+b5a92acf079ced6f80dd3e826ef1fec96eb2c1c0