add likely stub code for adding linkage to libole when building libpbd on windows.

I may have gotten the precise linkflags string incorrect, but this my best guess.

libs/pbd/wscript

@@ -148,6 +148,8 @@ def build(bld):
     
     if bld.env['build_target'] == 'x86_64':
         obj.defines += [ 'USE_X86_64_ASM' ]
+    if bld.env['build_target'] == 'mingw':
+        obj.linkflags += ['-lole']
 
     if bld.env['BUILD_TESTS'] and bld.is_defined('HAVE_CPPUNIT'):
         # Unit tests