Check to see if -ext o option is required to get compiler to write

Check to see if -ext o option is required to get compiler to write
foo.o instead of foo.c.o or foo.cc.o.  (MetroWerks)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@32168 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775