Fix typo: Caffe2_MAIN_LIB to Caffe2_MAIN_LIBS (#29746)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29746
I don't know if this actually broke anything because I just discovered
the typo while reading the cmake.
Signed-off-by: Edward Z. Yang <ezyang@fb.com>
Test Plan: Imported from OSS
Differential Revision: D18504546
Pulled By: ezyang
fbshipit-source-id: 6cb5fb1e71721e5cf8fc2f7b5552dc7c514f065f
