Describe the bug
When building project with vcpkg.json, mysql will not be enabled.
It seems libmariadb was built, but the macros in DbClientManager may not be properly set.

To Reproduce
Create an empty project with the following files:
vcpkg.json

{
  "name": "test",
  "version-string": "0.1",
  "port-version": 1,
  "homepage": "https://github.com/kotori2/test",
  "description": "Test",
  "dependencies": [
    {
      "name": "drogon",
      "features": [ "ctl", "mysql", "sqlite3" ]
    }
  ]
}

main.cpp

#include <drogon/drogon.h>

int main() {
    drogon::app().createDbClient("mysql", "127.0.0.1", 3306, "test", "root",
                                 "root", 4, "", "mysql", false, "utf8");
    return 0;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.21)
project(test)

set(CMAKE_CXX_STANDARD 20)
find_package(Drogon CONFIG REQUIRED)

add_executable(test main.cpp)
target_link_libraries(test Drogon::Drogon)

Expected behavior

Screenshots
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Desktop (please complete the following information):
NA

Smartphone (please complete the following information):
NA

Additional context
vcpkg: e2a23177553d67ba633288876746b5a41b94a628
Drogon: v1.7.4 release