[pytorch][buck] tweak code analyzer e2e script
Summary:
- Add debug mode to include debug information.
- Move codegen comment to FB shell script (as it's only checked-in FB repo).
- Analyze lite-predictor instead of full-JIT as full-JIT BUCK target contains variable kernels thus pull in a lot more dependencies.
- Use pre-opt bitcode instead of pre-codegen bitcode - there is one special `callOp()` case in RNN.cpp where optimized bitcode has opname string and API body inlined together: https://fburl.com/diffusion/8rz6u4rg; pre-optimization bitcode should give more stable result.
Test Plan: - Tested the bash script with stacked diff.
Reviewed By: iseeyuan
Differential Revision: D21298837
fbshipit-source-id: be33e2db5d8cb0f804460c503e52beb0dcb4857f
