AppVeyor: Fix build with Visual Studio 2019, ARM64

Define PopulationCount64=1 when needed.

The errors were:
C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um\winnt.h
(6343,27): warning C4013: '_CountOneBits64' undefined; assuming extern
returning int

[skip ci]

Author: fxlb

.appveyor.yml

@@ -95,12 +95,14 @@ environment:
       PLATFORM: ARM64
       SDK: npcap-sdk
       REMOTE: -DENABLE_REMOTE=NO
+      POPULATIONCOUNT64: -DPOPULATIONCOUNT64=1
       # VS 2019, Npcap, 64-bit ARM, with remote
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
       GENERATOR: "Visual Studio 16 2019"
       PLATFORM: ARM64
       SDK: npcap-sdk
       OPENSSL_ROOT_DIR: -DOPENSSL_ROOT_DIR=C:\OpenSSL-v33-Win64\bin
+      POPULATIONCOUNT64: -DPOPULATIONCOUNT64=1
       # VS 2022, WinPcap, 32-bit and 64-bit x86, without remote
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022
       GENERATOR: "Visual Studio 17 2022"
@@ -167,5 +169,5 @@ build_script:
   - md build
   - cd build
   - cmake --version
-  - cmake %REMOTE% %OPENSSL_ROOT_DIR% -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -G"%GENERATOR%" -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -G"%GENERATOR%" -G"%GENERATOR%" -A %PLATFORM% ..
+  - cmake %POPULATIONCOUNT64% %REMOTE% %OPENSSL_ROOT_DIR% -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -G"%GENERATOR%" -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -DPacket_ROOT=c:\projects\libpcap\Win32\%SDK% -G"%GENERATOR%" -G"%GENERATOR%" -A %PLATFORM% ..
   - msbuild /m /nologo /p:Configuration=Release pcap.sln

CMakeLists.txt

@@ -656,6 +656,9 @@ endif(WIN32)
 if(MSVC)
     add_definitions(-D__STDC__)
     add_definitions(-D_CRT_SECURE_NO_WARNINGS)
+    if(DEFINED POPULATIONCOUNT64)
+        add_compile_definitions(PopulationCount64=${POPULATIONCOUNT64})
+    endif()
 endif(MSVC)
 
 if(USE_STATIC_RT)