[Bono Bump] Bump mono to pick fix for issue (xamarin#19389) (xamarin#…

…8258)

Commits:

* mono/mono@e77cea1 Fix Windows .msi build with recent cygwin updates.
* mono/mono@fda7399 Adding static to ss_req_acquire and ss_req_count.

Complete diff: mono/mono@beccf5b...e77cea1

mk/mono.mk

@@ -1,4 +1,4 @@
-NEEDED_MONO_VERSION := beccf5ba4386148534467bff03fabe92da6d9705
+NEEDED_MONO_VERSION := e77cea191052c67c97545221091b98351057f485
 NEEDED_MONO_BRANCH := 2020-02
 
 MONO_DIRECTORY := mono