Update to Gradle 3.2.

- Add gradle-3.2.bin.zip and gradle-api-3.2.jar (gradle-api-3.2.jar is
  generated using the gradleApi() method).

Change-Id: I3f835e742e4dec7d7a555ad0134ce0efc2e598ed
Test: cd tools && ./gradlew test
4 files changed