Watcom: Drop symfile linker option

Cleanup of Windows-wcl386.cmake in commit v3.1.0-rc1~693^2 (Watcom:
Cleanup Windows-wcl386 configuration, 2014-04-01) also introduced use of
the 'symfile' link option but did not mention it in the commit message.

There is no way to set the symbol file name of a target, so it is better
to revert that change.  It is easy to run 'wstrip *' if the symbols need
to be stripped, but it is very difficult to get the right names for the
.sym files to install with debug/rel_with_deb_info configurations.
Merge topic 'watcom-drop-symfile-option' into next

6b63942e Watcom: Drop symfile linker option