update_crate_tests: Remove cwd

Env.cwd is misleading as it captures the location of the crate/package
being updated. Move the detection logic to the Package class and rename
the attribute.

There is the expectation that before running soong_ui, cwd is set to
ANDROID_BUILD_TOP; and before running write_mapping, that cwd is set to
the package directory. Add comments to capture this.

Test: update_crate_tests.py in external/rust/crates/libc
Change-Id: I5c4f16afe0b92b7c85173e4149ee17dd39c773c2
1 file changed