[tblgen] Disable lsan weak hook when building with msvc

This change is to fix a link time error when building llvm with msvc.

MSVC's implementation does not support weak hook or lsan so this change
disables lsan's weak hook definition.
Only GCC supports LSan.

Tested with visual studio 2019 v16.9.6

Reviewed By: aaron.ballman, rnk

Differential Revision: https://reviews.llvm.org/D118162