[ffmpeg] use pkgconfig to get system dependencies for cmake

ports/avcpp/0002-av_init_packet_deprecation.patch

@@ -0,0 +1,16 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index a5fed05..7875b91 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -24,6 +24,11 @@ set (AVCPP_WARNING_OPTIONS
+      $<$<CXX_COMPILER_ID:MSVC>:
+        /W4>)
+
++# fixes vcpkg uwp failures due to /sdl
++if(MSVC)
++    add_compile_options(/wd4996)
++endif()
++
+ # -pthread sets also some useful compile-time flags
+ set(THREADS_PREFER_PTHREAD_FLAG ON)
+ find_package(Threads)

ports/avcpp/portfile.cmake

@@ -9,6 +9,7 @@ vcpkg_from_github(
     HEAD_REF master
     PATCHES
         0001-remove-problematic-compound-literal.patch
+        0002-av_init_packet_deprecation.patch
 )
 
 string(COMPARE EQUAL "${VCPKG_LIBRARY_LINKAGE}" "static" AVCPP_ENABLE_STATIC)

ports/avcpp/vcpkg.json

@@ -1,6 +1,7 @@
 {
   "name": "avcpp",
   "version-date": "2021-05-06",
+  "port-version": 1,
   "description": "Wrapper for the FFmpeg that simplify usage it from C++ projects.",
   "homepage": "https://github.com/h4tr3d/avcpp",
   "dependencies": [