message: Add javacopts to the build targets in the open source build.
  This is needed to build it with java 1.7, which breaks our build otherwise.
diff: +load("//tools/build_defs:javac.bzl", "JAVACOPTS_OSS")
  +
  licenses(["notice"])
  package(default_visibility = ["//tools/build_defs:internal_pkg"])
  -load("//tools/build_defs:javac.bzl", "JAVACOPTS_OSS")
  -
  java_library(
  name = "prf",
  + javacopts = JAVACOPTS_OSS,
  exports = [
  ":hkdf_streaming_prf",
  ":streaming_prf",
  @@ -22,6 +23,7 @@ java_library(
  java_library(
  name = "hkdf_streaming_prf",
  srcs = ["HkdfStreamingPrf.java"],
  + javacopts = JAVACOPTS_OSS,
  deps = [
  ":streaming_prf",
  "//java/src/main/java/com/google/crypto/tink/subtle",
  