ci: Disable caching in AppVeyor
Don't cache the external directory because it interferes with
cloning the googletest repo. If the cache gets restored, the
attempt to clone googletest fails.
We can revisit caching to improve build times later.
diff --git a/.appveyor.yml b/.appveyor.yml
index 3cb4eb9..dbb127b 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -18,11 +18,6 @@
PYTHON_PATH: "C:/Python35"
PYTHON_PACKAGE_PATH: "C:/Python35/Scripts"
-# Cache the external directory to improve build times.
-# If the appveyor config file changes, invalidate the cache.
-cache:
- - external -> .appveyor.yml
-
branches:
only:
- master
