Add -lole32 to link libraries.

This fixes a problem when compiling with mingw-headers version 3.3
where the use of SHGetFolderPath() expands to a call to CoTaskMemFree()
which is defined in libole32.dll:

/usr/x86_64-w64-mingw32/sys-root/mingw/include/shobjidl.h:29954: undefined reference to `__imp_CoTaskMemFree'

Kristian Høgsberg <krh@redhat.com>

J. Ali Harlow <ali@juiblex.co.uk>