move to new build system

cmake/libraries/flac.cmake

@@ -0,0 +1,37 @@
+if(PROJECT_ENABLE_FLAC)
+  if(PROJECT_BUILD)
+    find_package(FLAC ${FLAC_VERSION} REQUIRED)
+
+    add_definitions(-DPROJECT_ENABLE_FLAC)
+
+    include_directories(BEFORE SYSTEM
+      ${FLAC_INCLUDE_DIRS}
+    )
+
+    link_libraries(
+      FLAC::FLAC
+    )
+  elseif(NOT PROJECT_IS_MINGW OR CMAKE_HOST_WIN32)
+    ExternalProject_Add(flac_project
+      PREFIX external
+      URL ${PROJECT_3RD_PARTY_DIR}/flac-${FLAC_VERSION}.tar.gz
+      URL_HASH SHA256=0a4bb82a30609b606650d538a804a7b40205366ce8fc98871b0ecf3fbb0611ee
+      LIST_SEPARATOR |
+      CMAKE_ARGS ${PROJECT_EXTERNAL_CMAKE_FLAGS}
+        -DBUILD_SHARED_LIBS=${PROJECT_BUILD_SHARED_LIBS}
+        -DBUILD_STATIC_LIBS=ON
+        -DBUILD_EXAMPLES=ON
+        -DBUILD_PROGRAMS=ON
+        -DBUILD_TESTING=OFF
+        -DBUILD_DOCS=OFF
+        -DINSTALL_MANPAGES=OFF
+    )
+
+    set(PROJECT_DEPENDENCIES 
+      ${PROJECT_DEPENDENCIES}
+      flac_project
+    )
+
+    add_dependencies(flac_project vorbis_project)
+  endif()
+endif()