Summary: Provide a standalone path to compile and run a ExportedProgram in C.
Test Plan:
(1) Generate a compiled model from ExportedProgram
```
python generate_lowered_cpu.py --input-path /tmp/$USER/ep.pt --output-path /tmp/$USER/final.pt
```
(2) Compile a standalone test runner
```
TORCH_ROOT_DIR=/data/users/$USER/pytorch sh standalone_compile.sh standalone_test.cpp standalone_test.out
```
(3) Run test for the compiled model in step (1)
```
LD_LIBRARY_PATH=/data/users/$USER/pytorch/build/lib ./standalone_test.out /tmp/$USER/final.pt
```
Differential Revision: D66872380
Pull Request resolved: https://github.com/pytorch/pytorch/pull/142327
Approved by: https://github.com/hl475
