Simplify appveyor config

appveyor.yml

@@ -1,14 +1,14 @@
+configuration:
+  - Debug
+  - Release
+
 environment:
   CTEST_OUTPUT_ON_FAILURE: 1
   matrix:
   - BUILD: msvc
-    CONFIG: Debug
   - BUILD: msvc
-    CONFIG: Release
   - BUILD: mingw
-    CONFIG: Debug
   - BUILD: mingw
-    CONFIG: Release
 
 build_script:
   - python support/appveyor-build.py

support/appveyor-build.py

@@ -5,7 +5,7 @@ import os
 from subprocess import check_call
 
 build = os.environ['BUILD']
-config = os.environ['CONFIG']
+config = os.environ['CONFIGURATION']
 path = os.environ['PATH']
 cmake_command = ['cmake', '-DFMT_PEDANTIC=ON', '-DCMAKE_BUILD_TYPE=' + config]
 if build == 'mingw':