Add a -sha256 argument to soong_zip that computes SHA256 checksum for each file and stores the value in file header. The SHA information can then be used by downstream systems that use content addressing. Bug: 259513199 Test: zip_test.go Test: soong_zip -o test.zip -D test_dir -sha256 Change-Id: I20e9f424bd0a4604f0dc7cc77bd65f10eb49a163