MFC r347978:

Fix OptionalObsoleteFiles copy/paste mistake from r345236, which
connected libomp to the build. The comparison should not have been
against ${MK_OPENSSH}, but against ${MK_OPENMP}, obviously.

MFC r347979:

To avoid unnecessarily modifying ports, add a -lgomp symlink, since GCC
does not ship a -lomp symlink. Also update OptionalObsoleteFiles for
this, and add 32-bit variants while here.

Approved by: re (gjb)
Submitted by: jbeich
PR: 237975