revert r313473 (Disable LLD_IS_LD option combinations that fail)

revert r313473 (Disable LLD_IS_LD option combinations that fail)

r316647 corrected the build of tblgen and libllvm as dependencies for
LLD so undo the temporary seat-belt.

We still want to extend the build infrastructure to automatically detect
the case where the host LLD can be used instead of building a bootstrap
LLD, and likely extend libllvmminimal to meet LLD's needs for cases
where the build includes LLD but not Clang.

Sponsored by:	The FreeBSD Foundation