Prebuilt java_tools should have a filegroup that includes zipper

[timothyg-stripe]

Prebuilt java_tools zip files include the zipper binary:

❯ curl -L https://github.com/bazelbuild/java_tools/releases/download/java_13.6.1/java_tools_linux-v13.6.1.zip 2>/dev/null | tar -t | grep zipper
java_tools/ijar/zipper

This appears to be an intentional choice:

bazel/third_party/ijar/BUILD

Lines 138 to 143 in 4a5b523

	genrule(
	name = "ijar_deploy_zip",
	srcs = [
	":ijar",
	":zipper",
	],

But the BUILD file that comes with prebuilt java_tools doesn't have a filegroup with the zipper binary, so we can't directly reference it, which is unfortunate.

[fmeum]

I think that it lives under @bazel_tools//tools/zip.

[timothyg-stripe]

@fmeum @bazel_tools//tools/zip:zipper/zipper is only the current platform's binary. Ideally we'd like access to all platforms.