ci: Improve vcpkg binary cache settings

This change comes with two improvements:
1) using the VCPKG_DEFAULT_BINARY_CACHE variable drops dependency on
vcpkg default cached archives location, and improves readability
2) two obvious cases when binary cache is invalidated are defined, that
guaranties it won't grow boundlessly when, for example, vcpkg has being
updated.

.cirrus.yml

@@ -86,6 +86,7 @@ task:
     PATH: 'C:\jom;C:\Python39;C:\Python39\Scripts;C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\MSBuild\Current\Bin;%PATH%'
     PYTHONUTF8: 1
     CI_VCPKG_TAG: '2021.05.12'
+    VCPKG_DEFAULT_BINARY_CACHE: 'C:\Users\ContainerAdministrator\AppData\Local\vcpkg\archives'
     QT_DOWNLOAD_URL: 'https://download.qt.io/official_releases/qt/5.12/5.12.11/single/qt-everywhere-src-5.12.11.zip'
     QT_LOCAL_PATH: 'C:\qt-everywhere-src-5.12.11.zip'
     QT_SOURCE_DIR: 'C:\qt-everywhere-src-5.12.11'
@@ -121,7 +122,13 @@ task:
       - jom
       - jom install
   vcpkg_binary_cache:
-    folder: 'C:\Users\ContainerAdministrator\AppData\Local\vcpkg\archives'
+    folder: '%VCPKG_DEFAULT_BINARY_CACHE%'
+    reupload_on_changes: true
+    fingerprint_script:
+      - echo %CI_VCPKG_TAG%
+      - msbuild -version
+    populate_script:
+      - mkdir %VCPKG_DEFAULT_BINARY_CACHE%
   install_python_script:
     - choco install --yes --no-progress python3 --version=3.9.6
     - pip install zmq