Add windows JNI support (#44257)

Summary:
Fixes #32516

Pull Request resolved: #44257

Reviewed By: malfet

Differential Revision: D24332820

Pulled By: ezyang

fbshipit-source-id: 1dd97e9c8140129a02a9078623b190b33f30d5b0

.circleci/scripts/binary_populate_env.sh

@@ -100,8 +100,14 @@ if [[ "$PACKAGE_TYPE" == libtorch ]]; then
   POSSIBLE_JAVA_HOMES+=(/usr/local)
   POSSIBLE_JAVA_HOMES+=(/usr/lib/jvm/java-8-openjdk-amd64)
   POSSIBLE_JAVA_HOMES+=(/Library/Java/JavaVirtualMachines/*.jdk/Contents/Home)
+  # Add the Windows-specific JNI path
+  POSSIBLE_JAVA_HOMES+=("$PWD/.circleci/windows-jni/")
   for JH in "${POSSIBLE_JAVA_HOMES[@]}" ; do
     if [[ -e "$JH/include/jni.h" ]] ; then
+      # Skip if we're not on Windows but haven't found a JAVA_HOME
+      if [[ "$JH" == "$PWD/.circleci/windows-jni/" && "$OSTYPE" != "msys" ]] ; then
+        break
+      fi
       echo "Found jni.h under $JH"
       JAVA_HOME="$JH"
       BUILD_JNI=ON