Fix appveyor glm_DIR path

.appveyor.yml

@@ -81,7 +81,7 @@ test_script:
   - ps: |
       mkdir build_test_cmake
       cd build_test_cmake
-      cmake ..\test\cmake\ -G "$env:generator" -Dglm_DIR="$env:APPVEYOR_BUILD_FOLDER"
+      cmake ..\test\cmake\ -G "$env:generator" -Dglm_DIR="$env:APPVEYOR_BUILD_FOLDER/cmake/glm/"
   - cmake --build . --config %CONFIGURATION% -- /m /v:minimal
 
 deploy: off