ICU: CMake 4+ compatibility (#852)

Set `CMAKE_POLICY_VERSION_MINIMUM=3.5` to make the project work with
CMake 4+.

This fixes the following error:
```
CMake Error at CMakeLists.txt (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from CMake.

  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.

  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.
```

Author: NeroBurner

cmake/projects/ICU/hunter.cmake

@@ -5,6 +5,7 @@
 
 include(hunter_add_version)
 include(hunter_cacheable)
+include(hunter_cmake_args)
 include(hunter_download)
 include(hunter_pick_scheme)
 
@@ -107,6 +108,18 @@ hunter_add_version(
     506109ef6fa0c3105be64bcebb5bd9e3fba1a24f
 )
 
+if(HUNTER_ICU_VERSION VERSION_LESS 63.2)
+    # CMake 4.0+ compatibility with older ICU packages
+    set(_hunter_ICU_cmake_compatibility_flag "CMAKE_POLICY_VERSION_MINIMUM=3.5")
+else()
+    set(_hunter_ICU_cmake_compatibility_flag "")
+endif()
+if(NOT _hunter_ICU_cmake_compatibility_flag STREQUAL "")
+    hunter_cmake_args(ICU CMAKE_ARGS
+        ${_hunter_ICU_cmake_compatibility_flag}
+    )
+endif()
+
 hunter_pick_scheme(DEFAULT url_sha1_cmake)
 hunter_cacheable(ICU)
 hunter_download(PACKAGE_NAME ICU)