cmake: export mimalloc-static as well
cmake: export mimalloc-static as well

Otherwise a static only build would not be usable as cmake package
(as mimalloc.cmake wouldn't be generated).

Signed-off-by: akarin <042dc4512fa3d391c5170cf3aa61e6a638f84342@akarin.info>

microsoft/mimalloc,microsoft/mimalloc