Merge #20489: CI msvc: only build vcpkg dependencies for release (not debug) to reduce build times

fa18e7c This change to the appveyor CI config for msvc builds reverses a change introduced in #19960. It re-applies a setting to inform vcpkg to only build release vesions of the dependencies rather than the default of debug and release. (Aaron Clauson)

Pull request description:

  This change to the appveyor CI config for msvc builds reverses a change introduced in #19960. It re-applies a setting to inform vcpkg to only build release versions of the dependencies rather than the default of debug and release.

  It had been expected that the vcpkg manifest mechanism introduced in #19960 would do this automatically but it turns out not to be the case.

ACKs for top commit:
  MarcoFalke:
    ACK fa18e7c if green
  hebasto:
    ACK fa18e7c, AppVeyor build takes 5 minutes less.

Tree-SHA512: 427e7e78190c20e0d85dad9b29beed2b6fa13f99c6bc72bcc1839dfb51237a7cc785ab707b4f851c527c1bb0d3e7ebad9e640969e19d29778584bbaeec75cecf

Author: MarcoFalke

.appveyor.yml

@@ -24,6 +24,7 @@ install:
       git pull origin master > $null
       git -c advice.detachedHead=false checkout $env:VCPKG_COMMIT_ID
       .\bootstrap-vcpkg.bat > $null
+      Add-Content "C:\tools\vcpkg\triplets\$env:PLATFORM-windows-static.cmake" "set(VCPKG_BUILD_TYPE release)"
       cd "$env:APPVEYOR_BUILD_FOLDER"
 before_build:
 # Powershell block below is to download and extract the Qt static libraries. The pseudo code is: