Tests: Fix Plugin test for international characters on Windows

Build KWSys with `CP_UTF8` internal encoding so that we can dynamically
load modules by absolute paths that contain international characters.
This is needed now that KWSys DynamicLoader uses KWSys Encoding instead
of hard-coding `CP_UTF8` itself.

Tests/Plugin/CMakeLists.txt

@@ -15,6 +15,7 @@ set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${Plugin_BINARY_DIR}/lib/static)
 set(KWSYS_NAMESPACE kwsys)
 set(KWSYS_HEADER_ROOT ${Plugin_BINARY_DIR}/include)
 set(KWSYS_USE_DynamicLoader 1)
+set(KWSYS_ENCODING_DEFAULT_CODEPAGE CP_UTF8)
 add_subdirectory(${Plugin_SOURCE_DIR}/../../Source/kwsys src/kwsys)
 
 # Configure the location of plugins.