Bump VSmac min version to 7.7.0.1373

To pick up the fix for https://devdiv.visualstudio.com/DevDiv/_workitems/edit/658916/
Should fix the XM classic build failures

Author: lambdageek

Make.config

@@ -63,8 +63,8 @@ MIN_XM_MONO_VERSION=5.14.0.136
 MIN_XM_MONO_URL=https://xamjenkinsartifact.azureedge.net/build-package-osx-mono/2018-04/111/07c8f25fe536dbb7e244f965aa3f9a871f41e953/MonoFramework-MDK-5.14.0.136.macos10.xamarin.universal.pkg
 
 # Minimum Visual Studio version
-MIN_VISUAL_STUDIO_URL=https://download.visualstudio.microsoft.com/download/pr/11550896/783d2219a348f93b6988fb415951788a/VisualStudioForMac-Preview-7.4.0.985.dmg
-MIN_VISUAL_STUDIO_VERSION=7.4.0.985
+MIN_VISUAL_STUDIO_URL=https://bosstoragemirror.azureedge.net/vsmac/e3/e39c3dd97f72e6258af9de81163eccb7cfedcd08/VisualStudioForMac-Preview-7.7.0.1373.dmg
+MIN_VISUAL_STUDIO_VERSION=7.7.0.1373
 MAX_VISUAL_STUDIO_VERSION=7.7.99
 
 # Minimum CMake version