[llvm-debuginfo-analyzer] Fix linking errors in buildbots.

The tool used the 'old' LLVM build information (LLVMBuild.txt),
which caused linking errors in:

https://lab.llvm.org/buildbot/#/builders/177/builds/10125
https://lab.llvm.org/buildbot/#/builders/196/builds/19699

Update the CMake configuration to support the new LLVM build
system that uses only CMakeLists.txt.

Reviewed By: jryans

Differential Revision: https://reviews.llvm.org/D136159