aconfig: add support for cargo

Officially, aconfig is build using the Android tool-chain. However, to
speed up the local development cycle, add support for building with
cargo.

While it is possible to tell cargo to place the build artifacts outside
the source tree, there is no way to tell it to not generate the cargo
lock file in the same directory as Cargo.toml. Add a .gitignore to
ignore Cargo.lock and the target directory.

The way the Android build system and cargo generates code from the
protobuf files is slightly different. Tell cargo to enable the "cargo"
feature and introduce src/protos.rs to hide this difference from the
rest of the aconfig source.

Bug: 279485059
Test: m aconfig && aconfig
Test: atest aconfig.test
Test: cargo build
Test: cargo test
Change-Id: I85741f58cadae353ed95c124f566e4f4a7484186
5 files changed
tree: 9efee4833de0a888804755630f67542a0a8a2aa4
  1. common/
  2. core/
  3. packaging/
  4. target/
  5. tests/
  6. tools/
  7. .gitignore
  8. banchanHelp.sh
  9. buildspec.mk.default
  10. Changes.md
  11. CleanSpec.mk
  12. Deprecation.md
  13. envsetup.sh
  14. help.sh
  15. METADATA
  16. navbar.md
  17. OWNERS
  18. PREUPLOAD.cfg
  19. rbesetup.sh
  20. README.md
  21. shell_utils.sh
  22. tapasHelp.sh
  23. Usage.txt
README.md

Android Make Build System

This is the Makefile-based portion of the Android Build System.

For documentation on how to run a build, see Usage.txt

For a list of behavioral changes useful for Android.mk writers see Changes.md

For an outdated reference on Android.mk files, see build-system.html. Our Android.mk files look similar, but are entirely different from the Android.mk files used by the NDK build system. When searching for documentation elsewhere, ensure that it is for the platform build system -- most are not.

This Makefile-based system is in the process of being replaced with Soong, a new build system written in Go. During the transition, all of these makefiles are read by Kati, and generate a ninja file instead of being executed directly. That's combined with a ninja file read by Soong so that the build graph of the two systems can be combined and run as one.