Setting boost library mirror in a variable

3rdParty/boost/CMakeLists.txt

@@ -1,8 +1,8 @@
 Find_Package(Boost QUIET COMPONENTS regex)
 include(FetchContent)
 
-if(NOT DEFINED OPENCV_REPO)
-    set(OPENCV_REPO https://github.com/opencv/opencv.git)
+if(NOT DEFINED BOOST_LIBRARY_MIRROR)
+    set(BOOST_LIBRARY_MIRROR https://github.com/boostorg/boost/releases/download/boost-1.84.0/boost-1.84.0.tar.xz)
 endif ()
 
 if (NOT Boost_FOUND)
@@ -10,7 +10,7 @@ if (NOT Boost_FOUND)
     set(BOOST_ENABLE_CMAKE ON)
     FetchContent_Declare(
         Boost
-        URL https://github.com/boostorg/boost/releases/download/boost-1.84.0/boost-1.84.0.tar.xz
+        URL ${BOOST_LIBRARY_MIRROR}
     )
     FetchContent_MakeAvailable(Boost)
 endif()