Add instructions for building with bazel
Add instructions for building with bazel

https://github.com/google/dagger/issues/908

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=173117199

cgruber/dagger,google/dagger,cgruber/dagger,ze-pequeno/dagger,ze-pequeno/dagger,ronshapiro/dagger,ronshapiro/dagger,ze-pequeno/dagger,google/dagger,google/dagger,dushmis/dagger,cgruber/dagger,google/dagger,dushmis/dagger,ronshapiro/dagger,ze-pequeno/dagger