gcc-cross-intermediate: remove dummy libc.so *after* staging, since do_stage will...

gcc-cross-intermediate: remove dummy libc.so *after* staging, since do_stage will fail with "cannot find -lc" if it's removed beforehand.
This does contradict this part of the commit message of the previous change:
"This fix deletes the dummy libc.so before gcc-intermediate is staged. Because
the main purpose of dummy libc.so is to get gcc-intermediate built with shared
lib support. Ideally this libc.so should be deleted right after do_configure of
gcc-intermediate but gcc's configure is spread across and some configure stuff
happens during compile step. Therefore its best to delete this libc.so after
the compile step is done."
I don't have a better solution that this one.