Add skeleton code for a JNI .DLL on Windows.

Tested by hacking in a call to a JNI method into BatchMain.java .

--
Change-Id: I77b0731fa6b81f8cbc80cf2a31d427764fad6ad1
Reviewed-on: https://bazel-review.googlesource.com/#/c/3908/
MOS_MIGRATED_REVID=125955521

src/BUILD

diff --git a/src/BUILD b/src/BUILD
index b1434fe..bd277c8 100644
--- a/src/BUILD
+++ b/src/BUILD
@@ -8,7 +8,7 @@
     srcs = select({
         ":darwin": ["//src/main/native:libunix.dylib"],
         ":darwin_x86_64": ["//src/main/native:libunix.dylib"],
-        ":windows": [],
+        ":windows": ["//src/main/native:windows_jni.dll"],
         "//conditions:default": ["//src/main/native:libunix.so"],
     }),
     visibility = [