Try previous build image on AppVeyor

Mark-Simulacrum · pietroalbini · commit d8a026d3bf75 · 2019-04-24T23:03:44.000+02:00
diff --git a/appveyor.yml b/appveyor.yml
@@ -1,3 +1,7 @@
+# LLDB seems missing on the stable branch, while it's fine on the master
+# branch. This is a temporary fix to get 1.34.1 out.
+image: Previous Visual Studio 2017
+
 environment:
 
   # By default schannel checks revocation of certificates unlike some other SSL
