[pytorch][CI] end-to-end custom build script (#34012)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34012
Today some mobile simulator tests only run on landed PRs and it requires
setting up special build environment to repro errors locally.
The goal of the PR is to do end-to-end mobile custom build & integration
tests with host toolchain (using same CMake options as mobile build). This
way, non-mobile engineers can capture & debug mobile related build issues
much more easily.
There are three custom build types that this script supports:
1. `TEST_DEFAULT_BUILD=1 ./build.sh` - it is similar to the prebuilt libtorch
libraries released for Android and iOS (same CMake build options + host
toolchain), which doesn't contain autograd function nor backward ops thus is
smaller than full LibTorch.
2. `TEST_CUSTOM_BUILD_STATIC=1 ./build.sh` - it further optimizes libtorch
size by only including ops used by a specific model.
3. `TEST_CUSTOM_BUILD_DYNAMIC=1 ./build.sh` - similar as 2) except that it
relies on the op dependency graph (instead of static dispatch) to calculate
and keep all transitively dependent ops by the model.
Type 2) will be deprecated by type 3) in the future.
Type 3) custom build has not been fully supported yet so it's expected to fail.
Replacing existing mobile build CI to run Type 1) build & integration test.
Test Plan: Imported from OSS
Differential Revision: D20193328
Pulled By: ljk53
fbshipit-source-id: 48c14cae849fde86e27123f00f9911996c1cf40e
