ld: Rename a file on Windows fails if target already exists

To rename a file on Windows, the target name cannot exist. Removing file
prior to renaming ensures this is handled.
To remove a file on Windows, the file cannot be open. Closing the bfd
handle ensures this is handled.
Moved call to free on isympp / osympp to after bfd is closed to align
with comment earlier in the cmdline_add_object_only_section function.

Signed-off-by: Torbjörn SVENSSON <torbjorn.svensson@foss.st.com>